Bremer Loch, Bronze donation box at Market Square in Bremen, Germany

The Bremer Loch is a round bronze lid resembling a manhole cover, set into the pavement of Bremen's market square in front of the parliament building. A small hole at its centre takes coins, which fall into a steel container 91.44 cm deep and 50.8 cm across.

The Bremer Loch was installed in 2007 on the market square in front of the parliament building. It was the idea of the professor and designer Fitz Haase, who devised the collecting box for the Wilhelm-Kaisen-Bürgerhilfe, a foundation named after a former mayor of Bremen. By early 2017 the box had collected around 150,000 euros, and it takes in an average of 12,000 to 17,000 euros a year.

The four animal voices come from the Brothers Grimm tale of the Bremen Town Musicians, who never actually reached Bremen. Each coin triggers one voice only, so visitors often drop several coins to hear the donkey, dog, cat and rooster in turn.

The slot lies flat on the ground and is easy to spot right in front of the Parliament building, with no need to search around. You can use it at any time of day, as there are no barriers or restricted hours.

Beneath the bronze slot sits a steel bucket fitted with a light sensor that triggers the animal sounds the moment something passes through. The whole mechanism stays out of sight, hidden entirely underground.