Between the Glop and Church Square in Hoorn lies a special relic of the underground system of interceptor sewers and waterways. The Glop is a blind alley from Lange Kerkstraat. From the Glop the brick hall runs through under the Boterhal. Until the 60s of the twentieth century, this course is part of a large brick sewer system. Anton Construction & Concrete recently has been at work here. By placing access hatches and stairs, this piece of history can now be visited again by the public.