Romans built watchtowers along the Rhine (the border of the Roman Empire) to send messages to each other using light and sound signals in case of danger. It is likely that a real watchtower once stood in the vicinity of this artwork during Roman times.
The artist, Niels Albers, drew inspiration from Roman history and designed the artwork. The artwork is a tower that depicts the development of Woerden since Roman times, using the three points below. Hence the artwork's name, "3 Milestones."
The four poles symbolize the base of the watchtower, as Roman watchtowers also stood on four poles.
The tower's floor consists of a pentagon. In 1371, a pentagonal moat was dug around the then village of Woerden. The excavated soil was used to build a rampart, turning it into a fortified town with a moat. The rampart was likely reinforced with poles.
The walls of the tower are inspired by Woerden's current street pattern. The pattern is folded upward on all four sides.
The artwork is not in good condition. It's fenced off to prevent people from climbing in via the stairs. This is perfectly understandable. The upstairs floor is rotten and desperately needs to be replaced. Hopefully, this will happen, as it's a remarkable work of art.