In the 20th century, the North Vietnamese military had its headquarters within the Citadel, coded D67. A connecting underground tunnel allowed for emergency evacuation in case of an attack.
Construction work for the National Assembly building in 2003 uncovered extensive ruins the citadel dating back to the Thăng Long era. Many of the historical relics were removed to the Vietnamese History Museum. The archeological finds has halted the construction of the National Assembly building on the site, pending additional excavations.
Lenin
Main Building
View from the main building
Hard to tell but that's a US quarter.