The site of the fortress is identified by some scholars with ancient Kanethos as scanty remains of buildings and graves are preserved on its surface. The hill was probably fortified in the Roman period but it was certainly not fortified in the Byzantine, the Venetian and the early period of the Turkish occupation. The castle now seen was probably built by the Turks in 1684 in order to protect Chalkis from the Venetians. It was designed by the Venetian Gerolimo Galopo and its architectural form is more European than Turkish in character. The fortress was unsuccessfully sieged by the Venetians of Morozini in 1688 and the Turks managed to keep it until the Greek liberation when they gave it over to the Greek state.
The castle of Karababa lies on a hill of the boeotian coast, called Phourka. It occupies a strategic position, overlooking the straits of Euripos and the town of Chalkis. Since it was designed by a Venetian, it is almost purely Venetian in form. The enceinte is oblong in plan, oriented E-W, strengthened by a rampart along the north wall, three bastions and one large tower. The south part of the wall is preserved in a poor condition. Ancient spolia are built in several parts of the walls.
The most complicate, hexagonal bastion is located on the east side of the wall, towards Chalkis. Two Russian canons of the 19th century are seen on the battlements. The only gate of the castle is on the SE side of the wall. Buildings of military function were built around the gate.
At the east curtain wall, between the gate and the east bastion, is a bell-tower, built in the place where an alarm bell of the fortress once stood.The only building preserved intact along the perimeter of the walls is a church dedicated to Prophetes Elias, dated to 1895.The west end of the enceinte is occupied by a seven-sided tower, the most substantial of the defensive structures of the fortress. Access to the tower is through a narrow vaulted corridor reminding a labyrinth.