Austrian explosives experts began on Wednesday blowing up 18 tonnes of unexploded ordnance from both world wars found around the country since the beginning of 2017.
First to go up at the Allentsteig military training ground was a 500-kilo (1,100-pound) bomb dropped by a US aircraft in World War II and three tons of hand grenades.
More than 70 years after World War II and a century after World War I, unexploded bombs still regularly turn up across Austria and Germany, often during construction work.
Earlier this month German authorities had to evacuate thousands of people after a World War II bomb was found near Berlin's main train station.
Last year, 11 tonnes were recovered from Austrian lakes and rivers and 659 kilos in the mountains dating from fighting between Austrian and Italian troops in World War I.
"Hand grenades can turn up a metre away from a path in the middle of Vienna," said Werner Tobisch from the EMD bomb disposal authority.
It blows up ordnance twice a year at Allentsteig -- also home to a large World War II German military cemetary -- north of Vienna.
Local wildlife has become used to the noise, with rabbits returning to hopping around several minutes later, Tobisch said.
The start of the two-day operation on Wednesday was watched at a safe distance in a bunker by Austria's defence minister, journalists and others.
Debris landed up to 1,000 metres (yards) away, craters as deep as five metres (30 feet) were left behind and the shock waves could be felt in the bunker, the Austria Press Agency reported.