Ho dynasty citadel was built in the reign of King Ho Quy Ly in 1397 with very big and solid green stone blocks and unique architecture in Vinh Loc district, Thanh Hoa Province.
The square citadel is also known as Tay Do with each edge 500m long and surrounded by a deep trench. The citadel has 4 gates, one in the east, west, south and north.
The citadel southern gate still maintains curved archways made with 3 green stones. The remaining citadel walls are made of earth. In the citadel, there remain many vestiges of an ancient palace.
The previous ancient citadels of Vietnam such as Hoa Lu, Co Loa are made of earth but Ho dynasty citadel was built with big stone blocks and is one of very few stone strongholds left in the world.