Alter Zoll, Bastion at Rhine River bank in Bonn, Germany

Alter Zoll is a bastion built from heavy stonework on the bank of the Rhine in Bonn, Germany. Old cannons are displayed on the grounds, and the open terrace faces the river directly.

The Bonn city wall dates from 1244; in 1642 it was reinforced and a bastion, today's Alter Zoll, was built at the toll site. The passage for the towpath survived as a casemate about 40 m long, 4 m wide and 4 m high, used from 1701 to 1703 as a powder magazine holding 150,000 pounds. The sandstone casemate gate of 1650 remains on the south side.

The name Alte Zoll refers to the former customs role of the site, but the structure itself is a bastion also called Dreikönigen. Since the 19th century it has been a viewpoint celebrated in travel literature; Goethe noted on 27 July 1815 that one could hardly resist trying to describe the Rhine view. Today boule players meet just south of it, and summer Stadtgarten concerts take place on the adjacent square.

The site is easy to reach on foot and open throughout the day, with outdoor benches and green areas where you can sit. The late afternoon tends to offer a clearer view across the river as the light shifts westward.

The two French salute cannons on the bastion were cast in 1803 and 1841 and given to the University of Bonn by Kaiser Wilhelm I after the victory of 1871; they were placed here and have never fired a live round. The small projecting stone ledge with two corbels near the corner is part of the bastion's weathered face.