Hungarian authorities evacuated around 1,000 people on Thursday after an unexploded World War II shell was discovered embedded in the roof of Budapest's city hall.
"The Soviet-made explosive device was found during a renovation project," a defence ministry spokesperson told state newswire MTI.
Workers, residents and tourists were evacuated as a precaution from the area surrounding the building in downtown Budapest.
Cites and towns across Nazi-allied Hungary were bombed heavily during the final months of the war by US, British or Soviet forces, with Budapest carpet-bombed on 37 occasions.
Many devices were buried in the ground after failing to explode and are often discovered during construction work, leading to 11 evacuations in the capital alone since 2008.
On Tuesday, a 70-kilo (154-pound) German bomb from World War II was unearthed at a construction site near the Royal Palace in Budapest's heavily touristed Castle district.
Last October, a 500-kilo (1,100-pound) US-made bomb was discovered in the river Danube close to a railway bridge in the north of the city.