Wandseteich Pond

The "wall pond" is a retention basin and the largest body of water in the Stellmoor tunnel valley. The Wandse Dam, which was built in the 1950s, dams the irregular water loads of the river and only slowly releases it to the lower reaches. In this way, it carries water longer than under natural conditions. The disadvantage of the retention basin: its water heats up considerably, which makes life difficult for typical river creatures in the lower reaches.

The Höltigbaum is crossed by the Wandse, a tributary of the Alster. Since the original source was diverted, the Wandse is now fed exclusively by the low water in the surrounding area. The Wandse in the Höltigbaum therefore only carries water from time to time and usually dries up as early as May. Only after the confluence of the Stellmoor spring river does the Wandse change into a steadily flowing river.

hoeltigbaum.de/fileadmin/Downloads/PDF/GletscherspurBroschre_2011.pdf

Beware of the narrow barriers England of the lake. Here you have to get off.

Unfortunately, the lake is now fenced in so that you cannot get any closer.
Before that, you could see frog spawn, leeches or other interesting animals up close.
Maybe it's better for the animals that way.