These are photos of the ancient sarcophagus which has found a secondary (at least) use as a water tank. The source of the water are subterranean springs or waterflows which are collected this point. The area is also the headwaters for the brook which starts at Aloupi and runs above ground down to the peripheral road and joins the concrete drainage channel that runs beside the road. At Episkopi the water goes under the road and finally meets the “river” inland from Agios Riganaki (T-junction).
The sarcophagus appears to be from the late Hellenistic to early Roman period (from 100 BCE or so). It is constructed from high quality marble and carries the “strigil” motif along with lion’s legs and paws at the corners.
Both photos enlarge by clicking
skopelosnews 
The strigil pattern is found on a lot of Roman and later, in early Christian sarcophagi.
See http://webapps.fitzmuseum.cam.ac.uk/explorer/index.php?oid=65515
Some say that the pattern signifies the “water of life”.