diệm commissioned the construction of three extremely deep tunnels leading from the palace to other parts of the city so that he and important government officials/military figures could escape in the event of a coup. during the 1963 coup d'etat, diệm is widely believed to have used one of these escape routes to escape the siege on the palace, which caused considerable damage. he fled to a supporter's house in cholon but was captured and executed a day later. the successor presidents still worked there until the completion of re-built independence palace, in 1966. the tunnels were 2.2 m high, with cast reinforced concrete (170 kg of iron / 1 m of concrete). walls were 1 m thick, with 6 iron vault doors for entry and exit. the tunnels had 2 downward stairs, leading to a basement with 6 rooms totalling 1392.3 m², which included conference rooms, offices, bathrooms, electrical rooms. the presidential office and presidential adviser's offices were equipped with battery banks for uninterruptible power supply, portable radios, rca transceivers. there are two exit tunnels that run towards le thanh ton street as well as six ventilation holes and numerous sewage drainages.