Bomb disposal experts were meant to detonate a 500-kilo bomb near Cologne university at around midnight.
But crowds of curious onlookers and drunken revellers caught wind of what was happening and gathered to watch, camera phones at the ready.
Lots of thrill-seekers even hid out of sight of the police, so they could get even closer to the blast.
It took officers an hour to find them all - finally giving the go-ahead at 1.09am on Friday, an hour-and-a-half after the planned explosion time of 11.30pm on Thursday.
Construction workers found the British bomb on Thursday while working on a building site near the university's main 45-storey building.
Around 5,000 people had to leave their homes as disposal experts were rushed to the scene.
The actual explosion was less dramatic than the onlooking “catastrophe tourists” were expecting. But it did make a four-metre-deep, eight-metre-wide crater.
Cologne's state of North Rhine-Westphalia is littered with bombs left over from World War II.
In 2012, there were 706 controlled explosions or de-fusings of bombs. More than 239 of these bombs weighed over 50 kilos.