Glaswaldsee Dam

partly from 1846 which is still in service

Like other karst lakes in the Black Forest in the 17th to 19th centuries, the Glaswaldsee was used as a reservoir (surge) to enable timber rafting. For this purpose, the water in the lake was dammed and filled with felled tree trunks. Once the lake was sufficiently full, the drain was opened and the logs were led downwards towards the valley. From here the wood from the Black Forest went over the Rhine to Amsterdam. There the wood from the mighty fir trees was used as masts for Dutch ships; large parts of the city of Amsterdam are built on wood from the Black Forest.
In order for the rafting to work and for the logs to be carried along, the Seebach leading into the valley had to have enough water. The Fürstenberg Forestry Office therefore built a wooden dam early on, but unfortunately we couldn't find out exactly when. However, since the lake was already used as a reservoir when it was surveyed in 1650, there must have been a dam with a lock at that time.
In 1846/47 the wooden construction was replaced by the stone wall that still exists today, and the built-in wooden lock was already in 1862. In 1978 the wall was reinforced with a concrete apron and the Glaswaldsee was drained.

Rafting in the lake, and indeed in the entire Wolftal, came to an abrupt end on June 2nd, 1887, when a devastating flood destroyed all the equipment needed for rafting that day.
Source: schwarzwald-informationen.de/glaswaldsee.html

You can walk along the dam, interesting stones with signs, inscriptions.