The Roman Fish Tank at Makrys Gialos (Mytilini)

A built Roman era rectangular fish tank is located at Makrys Gialos (Mytilini) with dimensions 6.60×5.50 m and height presently at 2.18 m. Its water-tight walls were built in accordance with the opus pseudosiodomous building system with rectangular volcanic stone blocks. It has been suggested that this tank contained fish and this is mainly supported by the presence of a duct along the interior faces of the walls with a number of rectangular sockets for a vertical copper or mesh fence with which it is believed that this tank was divided into smaller areas, assigned to different fish species to facilitate fish consumption and the resolution of practical issues such as cleaning up the tank. The supply and renewal of sea water was effected through a built rectangular open duct with reinforced walls. The interior sides of the ducts were discovered to have grooves with notches upon which vertical metal or wooden barriers would slide, which regulated water flow and replenishment. After obsolescence of its original use, the tank was filled with soil, sand and used ceramics. This tank was sealed by a transverse wall and the building was transformed into an H-shaped propylon.