Wikipedia
Gerulata
Gerulata was a Roman military camp located near today's Rusovce, a borough of Bratislava, Slovakia. It was part of the Roman province Pannonia and built in the 2nd century as a part of the Limes Romanus system. It was abandoned in the 4th century, when Roman legions withdrew from Pannonia.
Today there is a museum, which is part of the Bratislava City Museum.
The best preserved object is a quadrilateral building 30 metres long and 30 metres wide, with 2.4 metre thick walls.