The Ho Dynasty Citadel (Thành Nhà Hồ), a UNESCO World Heritage Site since 2011, is one of the finest surviving examples of stone military architecture in Southeast Asia. Located about 50 kilometers west of Thanh Hoa city in Vinh Loc District, the citadel was the capital of the short-lived Ho Dynasty (1400–1407) and was built in an unusual style: massive green stone blocks, each weighing several tonnes, fitted together without mortar in near-perfect alignment.
The outer walls stand up to eight meters high and run for nearly a kilometer on each side. The four stone gateways, particularly the south gate, are remarkable pieces of construction — the lintels are single stone blocks weighing up to 20 tonnes. The site is largely unrestored and much of it remains agricultural land, which gives it a genuinely archaeological quality that the more famous citadels in Vietnam have lost to renovation. Getting here requires a bus from Thanh Hoa city to Vinh Loc town, then a short motorbike ride to the site.