The cave is located 4 km northeast of Katochi and Neochori. Its mouth is on the south side of an long tree-lined hill, at the eastern end of the village of Mastrou. Its entrance is gained by a staircase. Within, it is limited to a single chamber with a natural underground pool of water. It has been subject to robbing and to intensive modern use, resulting in its significant deterioration.
In 2016, a brief survey conducted by the Eforeia of Palaeoanthropology and Speleology at the entrance of the cave revealed valuable evidence of its use in antiquity as a sanctuary which was located near the river Acheloos and where believers deposited their offerings. The existence of water inside it may have indeed been associated with purification and healing.
The focus of the worship took place on the edges of the natural underground lake. The earliest finds date to the beginning of the Iron Age, while cult use peaked in Archaic and Classical times (6th-4th centuries BC) and lasted until the Roman period, as is shown by clay busts, sets of votive figurines, vases and lamps, models of shoes or objects made of bone and glass. Some heads with holes in them, which were obviously depictions of worshippers or representations of the worshipped gods, may have been hanging inside the cave. One of these deities was probably Artemis, whose place of worship was often near lakes, marshes, coasts or harbours. Outstanding finds include figurines of dancers of various types, forming circular dance groups, or shells, probably offerings of fishermen praying for a good catch. The pottery found in the excavation suggests that communal meals took place at gatherings of the faithful at the sanctuary.
In the wider area of the cave is located Paianion, an ancient city dedicated to Apollo (Paianion – of the Paian), where there was a sanctuary to the god. Its remains are found today on the Palaiokastro hill, north of the village of Mastrou, in the centre of Paracheloitis, near the road from Gouria to Aitoliko. Remains of a fortified enclosure are preserved there, which extends for 850 m and follows the top of the hill. It has many angular projections and towers, characteristic of the late 4th – 3rd centuries BC. It is preserved in fragments, and within are traces of public buildings. The ancient sources testify to its total destruction by Philip V in 219 BC and the transfer of its building material for the construction of the fortifications of Oiniades.
The cave of Mastrou, as well as ancient Paianion, are not archaeological sites open to visitors. Finds from the cave are exhibited in the Xenokrateion Archaeological Museum.