Built between the 9th and 10th century, the Basilica de San Francesco is itself an architectural masterpiece that has been recognized the world over as one of the most lovely old world churches still in existence and is a UNESCO protected landmark, but perhaps the most remarkable feature is the basement crypt which has been flooded by the surrounding marshes and is now a shallow, underground goldfish pond. 

The lovely crypt is a model of religious burial design of the time, with lovely vaulted ceilings sloping into rows of stone columns and a floor that is inlaid with intricate mosaic tile patterns. Built along with the church in the 10th century, the crypt remains in strikingly well preserved condition. Some of the mosaic tiles have disappeared, but most of the remainder have been saved thanks to restoration efforts in 1977. The site is said to hold the remains of the terrifically named Bishop Neon who operated in Ravenna during the 5th century. 

Unfortunately the city of Ravenna sits on relatively soft marshland which has led to a number of structural issues among its buildings, and claims that the entire city is slowly sinking. This is certainly the case at the crypt which is now constantly filled with a foot or so of standing water. Since fighting the creeping flood has proved fruitless, the pool is now home to goldfish (and occasionally ducks) which swim among the columns and over the sunken mosaics. 

Visitors often even throw coins into the water, assumedly asking for wishes or good luck, although since this is still essentially a grave, it is anyone's guess who will be answering those requests.