The city centre of Vianen is still home to many of the medieval fortifications, such as the city moat, the city walls and the Lekpoort. The Lekpoort is the only city gate still remaining after parts of the city wall and gates were demolished in the 19th century, when they were seen to be impeding the increasing traffic.
The Lekpoort dates back to the 15th century. Its tower originally housed a prison.