Obertor is the only preserved gate of the 13th century fortress wall. Initially there were six of them. It is located in the south of the historical centre. An important trade route passed through Obertor, connecting Neuss with Cologne. In 800 years the gate with two strong round towers built from basalt and tuff have survived both the siege by Charles the Bold in the 15th century and wars of the 16th century.
Today Obertor hosts the department of medieval history of Clemens Sels museum. The museum was founded in 1908 upon the testament of Sels’s widow who bequeathed her entire fortune and a collection of art items to the local historical society. In 1950 the museum moved to Obertor. The museum fund grew, and in 1975 it received another building. Besides archeological findings of Ancient Roman and Medieval periods the museum can also boast of a considerable collection of paintings of German, French, Belgian and Dutch painters of the 17th-20th centuries. The most interesting collection includes works of symbolists and expressionists.