Ravenna is built on sand. Sand. And under the sand, there’s gas. And since World War II, (maybe eve before that, but it’s certainly been documented since then) the land has been slowly sinking. Mainly because the gas is being removed from underground. Anyway, the interesting thing is that maybe finally the subsidence (when the ground sinks) has stopped on the mainland – it is continuing on the coast but in downtown Ravenna it seems to have stopped.
The beautiful church of San Francesco, splat in the center of town, is a wonderful example of what subsidence can do. Many tourists go in and walk around, but few see that by just slipping a coin in a badly placed machine you can turn on the lights in the crypt. And if you lean over the railing and look down, you’ll notice that there’s about a meter of perfectly transparent water covering the delicate mosaics below. And if you wait a minute, you’ll probably notice that there are fat orange goldfish that look as if they’re flying over the mosaics and the coins that people superstitiously throw in . Because Ravenna isn’t only famous for its byzantine mosaics, its coastal night life and its subsidence. It’s also famous for its mosquitos.