Some 600 people were evacuated from their homes in Frankfurt as bomb disposal experts could remove a World War II-era bomb.
According to media reports, the bomb was defused underwater on Sunday, leading to a loud detonation and a big water fountain.
The 250 kg bomb was detected by divers with the city's fire service during a routine training exercise in Frankfurt's River Main.
Even more than 70 years after World War II, bombs and other munitions are still detected in several parts of Germany.