The "Green Classroom" in Ulm is an experiential learning forum outside school. Its educational concept is based on experimental learning and is geared towards expanding biological knowledge and developing environmental attitudes regarding preservation and utilisation of nature. We assessed the environmental attitude of 92 students before and after they visited the "Green Classroom", and compared the answers they gave in their questionnaires with those of 100 students from a control group. Although the students spent only one morning in the "Green Classroom", attitudes towards utilization of nature improved after their visit but not towards preservation of nature. Moreover, students displayed greater intrinsic motivation towards learning about the animals than the control group. (Contains 2 tables and 1 graph.)