Tafkos is a cave in Rethymno prefecture at the foothills of , located at an altitude of 135 meters at the site Lago, close to Erfi.
Historically known to local residents, who explored it down to the first 300-400 meters, where the lake lies, in order to find a way to exploit the water supplies, Tafkos was first fully explored in 1990. It is considered one of the most impressive underground rivers with constant water flow. Along with another underground river, the “Water Manna” at the site Bourlakiana Agiasmatsi, it comprises an underground water system. Although speleological investigations have not resulted that there is a physical union between the two caves, it is certain that they communicate through a system of narrow passageways that fork among them and throw their waters to the surface, into the Prinias torrent.
Tafkos was formed in marly sandstone-biogenic limestone and has rich stone decoration of all kinds in different places and throughout the length of the cave, such as stalactites, stalagmites, columns, flowstones and helictites.
The today efforts of the residents of Erfi to draw the underground waters came off in 2000, with a well that pumps up water from the lake that lies approximately 400 meters far from the first entrance to the cave Tafkos.