"A visitor has discovered a grenade in a dried-up stream bed in Lainzer Tiergarten. She immediately reported it to the police," the law enforcement said on Twitter.
An explosives expert of the Vienna police determined that the grenade had been manufactured in the Soviet Union. The mine clearance service of the Austrian armed forces was notified, while the police cordoned off the area. The military has now removed the hand grenade from the reserve's territory, according to the statement.
There are reportedly still thousands of bombs from the World War II remaining unexploded across Europe, despite the authorities' attempts to get rid of the dangerous legacy. The Austrian military blows up the unexploded ordnance twice a year at the Allentsteig military training ground to the north of Vienna.