But we have to allow for a little more complexity in this story about the evolution of the Primitive Hut. 

In ancient Greece there was also a tradition of a small, round, stone, one-roomed sacred building, which was thought to be the memory of earlier, simple, round, wooden, rustic huts. The stone version was dedicated to certain deities. Just as a home would have a fire at its center, so the dedicated versions had a fire. The small wooden source buildings would burn easily and so were not a safe home for a venerated idol of a god. This may account for the enormous extra effort that was needed to recast them in inflammable stone. 

✙ The oldest remaining building in Rome is one of these, the Temple of Hercules Victor. ✙ ✙The roofs of it and the other ancient round buildings are long gone. It is speculated that their roofs’ structural elements were of wood and built in the simplest possible way to roof a circle in wood⎼a flattened dunce cap. This we see as the reconstructed roof on the Temple of Hercules Victor.

The memory of this ancient building type resonated through the Classical tradition. An example in Rome is ✙ a pavilion in the gardens surrounding the Borghese Palace.But note that, unlike the reconstructed roof of the much earlier Temple of Hercules Victor, this has a domed roof. 

This is another step of the story: ancient Romans figured out that by laying up clay bricks in smaller and smaller rings upon the round beam they could create a dome—a roof that curved in as it rose, that was more like 1/2 of a sphere. The bricks could be covered with a coating of stucco to make a smooth surface which was suitable to be painted—a very important asset. Tiny bits of the painting have survived in the remaining examples. 

Next, an innovative way to bring light in and air out. As I mentioned, it is assumed that inside the remembered original hut at its center was a fire, so a smoke vent was wanted at the top of the roof. Once the Romans switched to clay bricks ✙ they could create a vent simply by stopping construction before they had reached the top. This left a perfectly round hole in the roof at its apex. Rain would enter, yes, but so would sunlight. It looked like an eye, and so to this day the round hole in the ceiling is called an oculus.

We see an example of this domed, round building that is 40 kilometers outside of the city of Rome, in Tivoli, where at the cool, higher elevations the Roman Emperor Hadrian built a country estate to escape the city’s summer heat.But such a dome was severely limited in size by its weight. So, the next step in the story is a spectacular innovation in materials: an early form of cement which was made from volcanic ash. This could be poured into forms with deep coffers in them, which would permit a dome much lighter than brick, and therefore to span a much greater distance. Actually, coffered cement also would have permitted them to form roofs of a number of highly plastic shapes. 

But the simplest structurally stable shape is the round dome, and apparently, this was the limit to their imagination⎼or taste.  

Surviving intact is Rome’s second oldest surviving building, ✙ the Pantheon: it is the best preserved of the world’s handful of ancient buildings and it is north facing. ✙✙ It still has the world’s largest unreinforced dome which was originally gilded! It has been written that the Pantheon is the first building whose interior was its focus, and that when Michelangelo entered it he said that it looked more the work of angels than humans. 

Save for the monumental entry door the only source of light is ✙ the huge oculus⎯a circular hole in the ceiling/roof piercing the center of the sphere. As the sun passes overhead it casts an elliptical bright light on the floor. The simple clarity of the building, the power of the room, and its beauty of execution make it beloved by all architects. At night, the 27-foot-wide oculus is a mysterious, black circle. I meditated in it as a Catholic service went on around me. 

The Pantheon and the Temple of Hercules Victor are the two the sole remaining intact buildings (excluding two tombs) from ancient Rome; saved from deterioration or destruction because each was consecrated early on as a church.✙ Composed of the simplest of Platonic solids, the interior of the Pantheon is a single, perfect sphere, except that the lower half of the sphere is swallowed up by a cylinder of the same diameter.

But how to create an appropriately grand entry to a large, cylindrical building? The shocking, and hugely influential solution that we find at the Pantheon is a mashup. ✙ The front bit of a traditional, rectangular Corinthian temple is simply stuck on front of the cylinder, providing cover from the weather, signaling where the front door is, and conveying grandeur borrowed from the language of temples that all ancient Romans knew.

This idea of sticking a bit of a Greek or Roman temple onto the front of a larger building at the front door is one of the most influential and enduring elements in the entirety of Western architecture. And it has the simple, obvious name of the Greek temple front. 

Buckingham Palace in London has three temple fronts on its front side. Very imposing, even if they are squashed almost flat.

The Pantheon’s resonance extends to the US where it was the direct inspiration for ✙ Thomas Jefferson’s beloved design for the Rotunda at the University of Virginia (1821).

Perhaps the greatest, albeit smallest, High Renaissance building is ✙ the Tempietto (1510) by Donatello Bramante, an updating of the tiny, round ancient shrines. ✙ ✙It [is inspired by the Roman temple of the Vestal Virgins, and] is a petite, perfectly round building consisting simply of a ring of 20 Corinthian columns surrounding a small, walled round room, topped by a drum and a dome.Bramante’s version was intended to mark the spot of the martyrdom of St. Peter, though subsequently it was concluded that the location was not correct.

Small as it is, it is as much a work of sculpture as of architecture, and it radiates the Renaissance perfection of Platonic solids. It was a radical work in its time and is a sublime example of the simple clarity of the high Renaissance. 

✙ Sketched in ink, quickly so as not to force my companions to wait for long.

✙ The interior focusses one’s attention upon a statue of St. Peter. 

✙ But the eye is also pulled up to the Tempietto’s domed ceiling. 

The utter serenity of the interior of a High Renaissance dome is distinct from the more ancient, coffered Roman domes or the later sweeping domes that I saw in other, buildings such as St. Peter’s Basilica. Bramante paired the dome’s ribs, which makes the ceiling become more prominent than it would were it divided by equally spaced ribs. And the surface of the ceiling between the ribs is painted a sky-like light blue, but subtly takes on a white glow as it climbs, and is decorated with a diagonal checkerboard of perfect, six-rayed stars which get smaller as they ascend. 

The effect is that the ceiling swells upward and dematerializes into what feels like an abstract view of the idealized celestial regions. And yet it is a perfect half-dome above the viewer, conveying the Renaissance humanist view that we are at the center of the universe.What could an architect design that is more perfect? 

BLACK But again and again, generations of architects feel bored by the innovations of the last generation and want to express their own creativity. After Bramante’s work the next generation began to introduce their own manner of quirks and personal ticks into Classicism. This became known as Mannerism, and the master of it was Michelangelo. We will return to him. By early in the next century, and Francesco Borromini’s career, Mannerism was passé. 

Borromini was of the generation that took the idea of altering the Classical vocabulary to a much greater degree. No longer were they content to insert within it discrete distorted and personal elements. Instead they subjected buildings to the forces of flow, as though a water course was coursing through stone, hollowing out eddies and wearing away curved banks. 

This liquid distortion of the elements of the Classical vocabulary is full blow in ✙ Borromini’s very first building, the Church of San Carlo all Quattro Fontane (1634). ✙ ✙ Young though he was when he designed it, nonetheless the Baroque quality of flow is utterly and perfectly encapsulated in it. My friend Gary Paul says it is the finest Baroque building. Characteristically, the chapel’s vertical surfaces subtly undulate, and the ceiling forms a psychedelic oval in shape, but all surfaces are white, which is a characteristic of the Baroque. The white dematerializes the surfaces⎯they do not make so much of a perceptual impression, and this permits the enclosed space itself to be better perceived. And what a sinuous, dynamic, but simultaneously serene, space. The undulating, white interior surfaces should permit the eye to focus on the officiating priest and the painting behind him, but I find that they become minor events within the luminous, almost subterranean grotto. 

[“Borromini is supposed to have said that the corner is the enemy of all good architecture, and certainly he almost always manages in some way to deny it.”]

✙ Its lot is cramped and irregular, and how Borromini carved the chapel out of it, and used up the leftover bits of space, is masterful. But the little lot forced him to locate the entry façade in an uncomfortable position on the street.  You cannot see the entrance head on at any distance, so it is not possible to fully enjoy ✙ the Baroque undulations of the architrave. I imagine that grated on Borromini. ✙