The zoo used to have a dolphinarium called the Aquaforum. At the time of its building, one of the most modern of its kind. Over the years, however, the infrastructure was considered far too small and dated. The zoo's urban location prevented any expansion and meant the society could not build a new one. In 1999 the two dolphins were relocated to the Duisburg Zoo in Germany because of the new national standards for exhibits, with the exhibit too shallow to keep housing dolphins. The Aquaforum now hold sea lions, which are much less demanding.