The Nevada Test Site (now called the Nevada National Security Site) was the primary location for U.S. nuclear tests, conducting over 900 tests, both above ground and underground.
Bikini Atoll was the site of Operation Crossroads in 1946, where the first post-WWII nuclear tests were conducted.
This was the primary nuclear test site for the Soviet Union. Over 450 nuclear tests were conducted, both underground and above ground.
This was the site of the Soviet Union’s largest nuclear test, including the infamous Tsar Bomba in 1961, the most powerful nuclear weapon ever detonated (50 megatons).
France conducted a series of atmospheric and underground nuclear tests at Mururoa Atoll.
Romania carried out several peaceful nuclear explosions for scientific research, although it has never publicly disclosed a military nuclear weapons program.