Pozzo del Merro is a fresh water dive site, located in Mentana, Italy. The maximum depth is over 150ft/46m.
Located just outside of Rome, Pozzo del Merro is an interesting dive and likely one that you will never have experienced before. Known quite literally as a “sink hole”, Pozzo del Merro is the deepest flooded cavity in the world. Thought to be at least 400 metres deep and with no visibility this is definitely a dive for experienced divers only. However if you like underwater photography and want to capture some truly unique pictures, this is definitely worth a try.
Info
http://italy.greatestdivesites.com/central_italy/rome/pozzo_del_merro