Masada was a fortified plateau, occupied and defended in the first Jewish-Roman War by Sicarii rebels. In 72AD, the Roman governor of Iudaea Lucius Flavius Silva headed the Roman legion X Fretensis and laid siege to Masada. The Roman legion surrounded Masada and built a circumvallation wall and then a siege embankment against the western face of the plateau, moving thousands of tons of stones and beaten earth to do so. Tradition holds that the garrison fired the buildings and committed mass-suicide just before the Roman assault, but archaeologists have found only 30 skeletons on the site.
Anyways... the place is just perfect for the ruinous first level of a huge mega-dungeon with entrances on multiple levels.