It is located in Tay Giai commune, Vinh Loc District, in Thanh Hoa Province, in Vietnam's North Central Coast region.
Tay Do castle is rectangular in shape. Its north-south side is 870.5 m in length and its east-west side is 883.5 m in length. There are four gates: one at the south (fore gate), one at the north (back gate), one at the east (left gate), and one at the west (right gate). The southern gate is 9.5 m high and 15.17 m wide.
The castle was constructed from stone blocks, each of which is 2×1×0.7 m size on average.
Except for its gates, the castle is mostly ruined.
The Citadel was inscribed on UNESCO World Heritage Sites on June 27, 2011.