Network of pools and caves lies deep beneath Rome's Coelian hill.

Archaeologists have discovered a network of lakes in an underground quarry beneath the foundations of a church on Rome's Coelian hill, according to a report in daily Italian newspaper Il Messaggero.
The labyrinth of tunnels and pools lies underneath the Passionist church of SS. Giovanni e Paolo, located off Clivo di Scauro, near the rear entrance to Villa Celimontana. The foundations of the basilica were built in 1100 over the vast Temple of Claudius, dating from the first century AD.
Beneath the remains of this temple lies the network of man-made lakes, which were quarried up until the fourth century AD. Over the last 1,600 years stalactites have formed over the pools whose crystal clear waters are “bacteriologically extremely pure” according to archaeologists. Measuring a depth of between eight and 1.5 metres, the pools are dotted along a route more than two kilometres long, reports Il Messaggero.
The excavations are being undertaken by speleological association Roma Sotterranea in collaboration with the city's archaeological superintendency and the church authorities of SS. Giovanni e Paolo.
Archaeologists, who say that further underground areas remain to be explored, have not ruled out that the material quarried was used to construct the Temple of Claudius, whose 180 x 200m site was larger than the Colosseum. Experts say that the extensive quarry under the Coelian hill - in the heart of ancient Rome - was unusual as such activity normally took place outside the city.

For more information about underground sites in Rome, see the Wanted in Rome guide.

Photos Il Messaggero