In the Apennine hills south of Bologna is the natural (if improbable) grotto called the Grotte di Labante. In the area nearby they used to quarry a type of sedimentary limestone called travertino, and the grotto is formed from this limestone. A spring flows from the nearby Chiesa di San Cristofano through this cave system and gathers in a small, clear pool. That pool sits by one of the cave’s two main entrances, which are linked by a relatively straight passage. A number of smaller side branches can be found winding…
