|Chartres, the western rose window|
It is time for a short history lesson:
In Louis Charpentier's book about Chartres Cathedral  he writes the Gothic style appeared suddenly around 1130AD and "In a few years it reaches its apogee, born whole and entire without experiment or miscarriage. And the extraordinary thing is that it had at its disposal master-craftsmen, artisans, builders, enough of them to undertake the construction of eighty huge monuments in less than 100 years."
Jean Gimpel in his book  tells a similar tale "In three centuries, 1050 - 1350, several million tons of stone were quarried in France for the building of 80 cathedrals, 500 large churches...... More stone was excavated in France during those three centuries than at any time in Ancient Egypt." And that was just in France. During the same period cathedrals were being built in England, Italy and Germany.
Where did this knowledge and understanding of design and construction come from? It is generally assumed it was brought to Europe by the nine (later ten) Knights Templar in the 11th or 12th century. But before any of the great European Cathedrals were built the Moors in Al Andalus (i.e. Spain) had built the Great Mosque of Cordoba, work starting in 784AD; the Alhambra Palace in Granada (originally Al Hamra - the 'red fort') in 889AD (and exensively renovated in the thirteenth century); and many more.
All of those buildings, and the Cordoba Mosque in particular, were built in accordance with the design principles as described at the beginning of this short essay. [3,4]
So the influences on the Cathedral builders of Europe were not necessarily confined to the returning Crusaders as our historians tell us.
Historians are mere chroniclers of conflict between various tyrants and, as such, tell only a part of the story. They appear to have little or no interest in the 'common people' nor the co-operation between peoples that is necessary for civilisation to flourish. They never tell us about the trade between nations or the exchange of ideas. The Roman Empire stretched from the north of England across the Mediterranean and into the Holy Land. We know that tin was transported from Cornwall to Rome as an essential ingredient for making bronze. We also know that spikenard oil came from the Himalayas and was used by Mary Magdalene to anoint the feet of Jesus. So 2000 years ago it seems that there were extensive trade routes stretching across the known world, from 'Britannia' in the west to India (and possibly even into China) in the east. What else travelled along those trade routes? Think of all the different languages along this ancient 'silk road' and all the interpreters and translators who were obviously essential to conduct this trade. What else did they exchange besides goods? They would be exposed to new cultures, new ideas, different philosophies. As an example, one such traveller was Bernard the Pilgrim (Bernardus Sapiens, Bernard the wise) who was a Frankish Monk who left a chronicle of his journeys around the Mediterranean and into the Holy Land. The date of his travels is unclear but it is said to be 875 - 871 AD i.e. long before the first Crusade. 
There must have been other Christian travellers during the first millenium but without feeling the need to record their travels and as monks or abbots or bishops they would look at things from a different perspective than traders and merchants and so bring back more esoteric knowledge.
It is clear from the two books cited [9,10] that the driving force behind all of this building work came from the Monasteries, pricipally the Benedictines and the Cistercians.  And the main figure in all this seems to have been Bernard of Clairvaux who had links with the Templars and the building of Notre Dame de Chartres. "when the first Christians arrived in Chartres, during the declining years of the Roman Empire, they found in the 'Druid grotto' within the Chartres butte a statuette of the 'Black Virgin'. It was believed to represent Isis. Chartres, according to Charpentier, was a center for religious worship older than Christianity itself." 
That is an intriguing statement because -"St Bernard of Clairvaux was a great devotee of the Mother of Jesus, and he wrote numerous hymns and sermons which he dedicated to her. He also wrote several sermons on the theme of the Song of Songs in which the Bride sings “I am black but beautiful, O daughters of Jerusalem." 
Bernard of Clairvaux was a Cistercian  and he introduced the cult of Isis into Christianity under the veil of the Virgin Mary.  Chartres was the first to be dedicated to the Virgin Mary (the first to be called Notre Dame.)
And so we come to the most mysterious of all the great Cathedrals; Chartres. Better minds than mine remain baffled by the cathedral and its many mysteries so all I can do is give my own reaction after visiting and to comment on some strange anomalies therein.
- The first and most striking inpression is of the light inside. I know that these are stained glass windows and they really are unique. They are not coloured glass which merely filter and colour the sunlight. The building seems to glow inside, an 'inner light' almost. Bathed in that glow, that light brings to mind Wordsworth's poem 'Intimations of Immortality' which includes the lines that everything seemed 'apparelled in celestial light'.
Charpentier explains that stained glass first appeared in Persia and was used in the European cathedrals for no more than 150 years or so and then disappeared as quickly as it had arrived. To this day nobody has been able to replicate the glass nor to work out how it was created. It was produced by Alchemy, that much derided ancient science, the forerunner of chenistry. Charpentier explains that there is something in sunlight which is damaging to organic material, for example in how fabrics fade in colour or how photos fade and of course how our skins are pigmented by prolonged exposure to sunlight. And yet there is something else in sunlight which triggers photosynthesis in plants. He speculates that the composition of stained glass somehow excludes the damaging rays while allowing the beneficial rays to pass. It was only recently that modern science has begun to understand the effect of light on matter in what is called quantum electrodynamics.  How did the glass makers know that? How did the cathedral builders know to include such glass? Could that knowledge be part of the 'secret' that was allegedly brought back from the Holy Land? Would they have known or witnessed or even been part of 'The Miracle of the Holy Fire' in the Church of the Holy Sepulchre?  It might help to explain those questions about light.
- In one of those windows is a tiny gap in one of the panes of glass which allows unfiltered sunlight to pass. On the floor of the nave there is a small paving slab set at an angle to all others and in it is a small gilded metal tenon. At noon on the summer solstice a shaft of sunlight strikes that small piece of metal causing it to shine. The precision of the builders in calculating and locating that single moment in time is astonishing. How did they do that?
I should add that there is a similar but much less spectacular demonstration of the same thing in the Cloisters of Durham cathedral. On the south facing arcade there is a small gap in the tracery of the stone work and on the wall and floor of the arcade is a line with an arrow head etched into the wall and an arrow head etched into the floor. A shaft of sunlight will strike the arrow head on the wall at noon on the winter solstice and the arrow head on the floor at noon on the summer solstice. I don't know when that was incorporated into the stone work, whether it was there from the start or a later addition. And of the thousands of visitors, I wonder how many have noticed it?
- On the floor of the nave is a very large labyrinth (47 feet in diameter, the same diameter as the rose window) The labyrinth predates Christianity and it first appeared on the Greek coins of Crete in the 5th or 6th century BC. and has appeared at other times and places in pre-history.  So why is there a labyrinth in a Christian cathedral? Not that it is the only one, there are others in cathedrals in France and Italy.
But follow the pathway of the labyrinth in Chartres from its entrance to the centre and you will have journeyed more or less 666feet. Surely not, that is the famous or infamous number of the beast in Revelation, the last book of the New Testament. But all is not what it seems because we are back to the subject of the sun and light: 666 is, or was in ancient time, the number associated with the sun.  This cathedral does not easily reveal its secrets or mysteries.
- The outside of the cathedral is equally unorthodox in its many statues adorning virtually the whole building. I cannot begin to unravel the iconography; among the identifiable Christian statuary there is, for example, a statue of a donkey on its hind legs and playing a hurdy gurdy. I haven't the faintest idea what that is supposed to represent! The best guide I think would be a book called 'The Mystery of the Cathedrals' by Fulcanelli.  I have not read that book but I have read his other book "Les Demeures Philosphales" and I understood about half of it and there were some thing which I found difficult to accept: he seems to have undue reverence for an x shaped metal bar securely stored in a climate controlled room somewhere in Paris, this bar being the standard measure for the French metre. That struck me as odd because the length of the metre has been changed four times, to my knowledge, since it was invented in 1790. Furthermore it is irrelevant as a standard of measure because it does not conform to either a human scale or a geodetic scale or even a cosmic scale unlike every other standard of measure in history.
I am on safer ground with the actual dimensions of the building. The north tower is 365 feet in height and is topped by a cast iron 'flag' in the shape of the sun thus indicating the solar calendar. The south tower is 28 feet shorter than the north tower and is topped by a cast iron 'flag' in the shape of a crscent moon thus indicating a lunar calendar.  So the towers represent the solar, masculine aspect of humanity and the lunar, feminine aspect. (I have seen a lot of older paintings of the Virgin Mary showing her standing on a crescent moon with her head haloed with gold stars.)
This is esoteric rather than Christian symbolism and, overall, the cathedral seems to be dedicated to the sun. This is usually explained by the spread of Christianity which would take existing sacred places of worship and adapt Christianity and Christian symbolism to the extant spiritual system in order to convert the people to follow Jesus. (See above how Chartres was built on a site originally used by Druids) This was how Christianity spread in South and Central America but, oddly enough, in North America there was no attempt to use existing sacred places.
- So what does it all mean, why is it built they way it is? The short answer is, I don't know. I have a lot of other information which I could have included here but how to tie it all together into a coherent answer is beyond me at the moment and a lot of it would just confuse things further. One thing I do know is the effect on me of these buildings, not all of them but most of them. They all generate a strange air of tranquility, calmness and the awareness that there is a connection between here and the not-here which all religions are attempting to describe, a connection between here and that strange place colloquially known as heaven. A feeling that we are not alone and that we are all connected to all that was, is and will be. I am not sufficiently eloquent to articulate this and I know that I am not the only one.
It is not just the sacred buildings which do that. I have felt the same 'harmony' in other places: in the Alhambra Palace of Granada or in the Cañón del Río Lobos in the middle of Spain http://www.nourishingobscurity.com/2010/11/canon-del-rio-lobos/ but also just sitting and watching the sun set into the Pacific ocean or visiting the amazingly peaceful setting of the Holystone/Lady's Well in the far north of Northumberland.
Charpentier, in his book, writes "... its [Chartres] architectural harmony remains intact, or little short of it and no man can boast, not even in a practical sense, that he leaves the cathedral at Chartres the same as he was when he went in."
"From harmony, from Heav'nly harmony
This universal frame began
From harmony to harmony
Through all the compass of the notes it ran,
The diapason closing full in man."
- John Dryden, A Song for St. Cecilia's Day, 1687
 Notre Dame de Paris
 Viollet le Duc.
 fractals in architecture
 fractal architecture could be good for you
 A Beginner's Guide to Constructing the Universe by Michael S.
 Hexham Abbey, the Night Stair.
 The Vampire Rabbit of Newcastle
 Coventry Cathedral
 "The Mysteries of Chartres Cathedral" - Louis Charpentier.
also - http://www.newinvisiblecollege
 "The Cathedral Builders" - Jean Gimpel.
 Bernard the Wise
 Monasticism -
 Bernard of Clairvaux and the black Madonnas
 Cistercian Order -
 This page has been translated from Portuguese but the meaning is
 The Miracle of the Holy Fire
 'Architecture, Mysticism and Myth' by William Lethaby ( see chapter
 The magic square of the sun.
 "The Mystery of the Cathedrals" by Fulcanelli -
"Fulcanelli suggests that, just like there is a series of mysteries
dwelling inside the Egyptian pyramids, there is occult knowledge inside
the architecture and engineering of Medieval Gothic cathedrals. He
believed these buildings were not only dedicated to the glory of
Christianity, but also to books that contained the philosophical,
religious, and social thoughts of our ancestors. Like any sanctuary,
cathedrals posses a hospitable origin and were meant to shelter to
anyone in disgrace."
 It should be noted that St Paul's in London measure 365 feet from
the floor of the nave to the tip of the cross on the dome.