32. The Campanile – bottom up
Venice is a city in a shallow lagoon. Basically a swamp. The hundreds of muddy islands that have been built on and are connected by bridges over the gaps between them – the canals – are sitting on a compressed clay layer at the bottom of the sea at the northern end of the Adriatic. It is not surprising that many of the buildings in Venice are wonky, the floors are uneven and the walls aren't straight. It is more surprising that any buildings stand here at all. It is a tribute to the ingenuity of early Venetians that they managed to invent building techniques that allowed immensely heavy structures like the Basilica to remain for almost a thousand years without collapsing.
The bottom layer of Venetian foundations is made up of close-packed pinewood pilings hammered into the clay. They don't rot because they are too closely packed together to allow water to circulate, which means there is no free oxygen that could support microbe activity.
The engineers who examined the foundations of the Campanile found that the pilings were as sound as when they were first put in. The building collapsed because those foundations were never intended to take the weight that the various iterations of the Campanile finally acquired, and in the end they could no longer support it. The original foundations were repaired, strengthened, and extended to better support a belltower of this size, and a hundred years later this equally heavyweight replica is still here.