Today's castle is Almourol in Portugal, on an island in the Tagus River. When the Portuguese reconquered this area from the Muslims in 1129, there was already a fortress on the spot. This was given to the Templars, who were responsible for the defense of the region. The rebuilt and enlarged the castle; according to a carved stone over the entrance, the rebuilding was completed by 1179. They held it until their order was dissolved in 14th century.
Oddly, I can't find any bizarre Templar legends about the place; perhaps the Templars do not occupy the same place in the Portuguese imagination as they do in northern Europe. Portuguese accounts emphasize the castle's part in their own master narrative, the Reconquista. After the Templars were disbanded, the castle passed to the Portuguese crown, and for a time it was a prison.
According to travel reviews, the interior is pretty much empty. The castle has been restored, but so far as I can tell, most of the stonework is original. (Unlike the more famous Guimaraes Castle, the "birthplace of Portugal," which has been completely remade into a fairy tale construction.)