Specifically, on Tuesday, January 21, explosive experts were called at the scene, as a day before construction workers found a 500-kilogram bomb near the river, in the western German city of Cologne.

When the bomb was found, a TV station and the opera house were evacuated during the defusing operation. Shipping on the river and air traffic overhead were also interrupted before the defusing operation got underway.

Moreover, authorities shut down a bridge across the Rhine, from where trains pass heading to Cologne's main train station. The suspension of traffic in Cologne led to delays in train services across all of Germany.

Almost 75 years after the end of the war, unexploded bombs are frequently found in Germany. Disposing of them sometimes entails large-scale evacuations as a precaution.