The Thang Long Impe­r­i­al Citadel was built in the 11th cen­tu­ry by the Ly Viet Dynasty, mark­ing the inde­pen­dence of the Dai Viet. It was con­struct­ed on the remains of a Chi­nese fortress dat­ing from the 7th cen­tu­ry, on drained land reclaimed from the Red Riv­er Delta in Hanoi. It was the cen­tre of region­al polit­i­cal pow­er for almost 13 cen­turies with­out inter­rup­tion. The Impe­r­i­al Citadel build­ings and the remains in the 18 Hoang Dieu Archae­o­log­i­cal Site reflect a unique South-East Asian cul­ture spe­cif­ic to the low­er Red Riv­er Val­ley, at the cross­roads between influ­ences com­ing from Chi­na in the north and the ancient King­dom of Cham­pa in the south.