Aachtopf

The Aachtopf (German: [ˈaːxtɔpf] ⓘ) is Germany's biggest karst spring, south of the western end of the Swabian Jura near the town of Aach.

The cave system has been explored since the 1960s, but as of 2020 only a small part has been discovered due to a large blockage after a few hundred metres.

The name Aachtopf is compounded from Aach (meaning "water" in Old High German); Topf can be translated as "bowl" and is commonly used for round, bowl-shaped springs.

The Aachtopf is a karst spring, south of the western end of the Swabian Jura near the town of Aach.

The spring is the source of the river Radolfzeller Aach, which flows southward into Lake Constance, and empties into the Rhine.

After 60 hours he was able to detect all three substances in the spring, as evidenced by "splendidly green, salt water with a distinct creosote taste".