The Bastille was an irregular structure, more hexagonal than rectangular. It sat on a 20-foot tall base exposed when the moat was not filled with walls of 78 feet high, making it about 100 feet tall. It was 260 feet long at its maximum footprint. It was 130-150 feet wide (ends, middle). Walls were about 10 feet thick at the base. Reference "George Washington's Liberty Key: Mount Vernon's Bastille Key -- the Mystery and Magic of Its Body, Mind, and Soul," pages 29-30, for discussion with diagrams from engineers and architects just before its destruction.