The national monument of Binh Son Tower, also known as Vinh Khanh Pagoda Tower or Then Tower, is located in the grounds of Then Pagoda in Binh Son Village, Tam Son Town, Song Lo District. This is a typical architectural work built during the Tran Dynasty (1226-1400). Binh Son Tower not only has architectural and artistic value but also high aesthetic value, and is considered a "precious gem of the national treasure".

A ceremony was held in the northern province of Vinh Phuc to receive certificates recognising the Tay Thien site and the Binh Son Tower as special national relic sites.