"The Ostend lido was created from a full clay pit, the shore areas of which were parceled out by the owner Mejer and leased to interested parties. The whole thing was called Strandpark Ostende. In 1935, the Wehrmacht intended, in connection with the construction of the barracks in today's Wilsonstrasse to set up a military bathing establishment on this lake. The then city of Wandsbek was sent forward for this purpose. It bought the area in November 1935 from the owner Mejer or his heirs, terminated all lease agreements and handed the area over to the Wehrmacht in 1936. They built the planned military bathing establishment there. After 1945, the military bathing establishment was opened to the public again as the Ostend open-air swimming pool, later the Ostend lido. In popular parlance, the name “Ostende” is often attributed to soldiers who used it to commemorate their stationing in Belgium The North Sea resort of Ostende was intended to be remembered. However, this attribution of the name contradicts the fact that the lake is already referred to as “The Great Sunny Lake” with the addition “Ostende” in the land map on which Mejer sold the site, i.e. the name "Ostend" is older than its use by Wehrmacht soldiers."
(Source: Wikipedia: Hamburg-Tonndorf. As of: March 1, 2021)
In addition to this information, it is very nice to drive around the lake and take the small paths towards Farmsen. There are small ponds inhabited by dragonflies and waterfowl.