The unique planetary Nonnweiler trail at a scale of 1-1 billion has its starting point on the dam in the Primstal valley. The model representation of our solar system is impressive, with a complete nine-planet model and the size of the planets and their distance from each other all being in scale. Walking along the lake for a stretch of 5.9 km will bring you past all the stations. The total distance around the dam is 11.5 km, returning to the start. At the starting point in front of the “Sun" the trail is explained on information boards. The models of Mercury, Venus, the Earth-Moon model and Mars follow on the dam. A slight climb to the reservoir circular trail takes you to Jupiter, the largest planet model. From there you can enjoy the magnificent views of the fjord-like lake. The trail passes Saturn and Uranus passes to the Primsvorsperre (upstream dam). Over the Primswehr (weir) the astronomical tour continues to Neptune and Pluto, the last planets of our system.