Middeleeuws kasteel gelegen op een klein eiland in het midden van de Tagus rivier. Het kasteel was deel van de verdedigingslinie gecontroleerd door de Tempeliers en een strategisch punt tijdens de Portugese Reconquista.

"The castle rises over a granite outcropping 18 metres (59 ft), it is approximately 310 metres (1,020 ft) long and 75 metres (246 ft) wide, in the middle of the Tagus River waterway, a few metres below its confluence with the Zêzere River in front of the town of Tancos.[2] Although access to the Portuguese National Monument and fluvial islet is free, visitors to the structure must pay an inexpensive boat-ride across the river (which is the only way for visitors to reach the castle)."