- African Underground
- Congo's Underground
- Egypt's Underground
- Kenya's Underground
- Sahara Desert's Underground
- South Africa's Underground
- Zimbabwe's Underground
- Asian Underground
- Afghanistan's Underground
- Cambodia's Underground
- China's Underground
- India's Underground
- Iran's Underground
- Israel's Underground
- Japan's Underground
- Kashmir's Underground
- Mongolia's Underground
- Russian Underground
- Saudi Arabia's Underground
- Tibet's Underground
- Turkey's Underground
- Vietnam's Underground
- Australian Underground
- Central American Underground
- Bahama's Underground
- Belize's Underground
- Costa Rica's Underground
- Guatemala's Underground
- Mexico's Underground
- Panama's Underground
- Puerto Rico's Underground
- European Underground
- Austria's Underground
- Crete's Underground
- Czechia's (Czechoslovakia's) Underground
- England's Underground
- Finland's Underground
- France's Underground
- Germany's Underground
- Iceland's Underground
- Ireland's Underground
- Italy's Underground
- Malta's Underground
- Norway's Underground
- Poland's Underground
- Romania's Underground
- Spain's Underground
- Sweden's Underground
- Wales's Underground
- Middle Eastern Underground
- North American Underground
- Canadian Underground
- United States Underground
- Alabama's Underground
- Alaska's Underground
- Arizona's Underground
- Arkansas's Underground
- California's Underground A-J
- California's Underground K - N
- California's Underground O-Z
- Colorado's Underground
- Connecticut's Underground
- Delaware's Underground
- Florida's Underground
- Georgia's Underground
- Hawaii's Underground
- Idaho's Underground
- Illinois's Underground
- Indiana's Underground
- Iowa's Underground
- Kansas's Underground
- Kentucky's Underground
- Louisiana's Underground
- Maine's Underground
- Maryland's Underground
- Massachusetts's Underground
- Michigan's Underground
- Minnesota's Underground
- Mississippi's Underground
- Missouri's Underground
- Montana's Underground
- Nebraska's Underground
- Nevada's Underground
- New Hampshire's Underground
- New Jersey's Underground
- New Mexico's Underground
- New York's Underground
- North Carolina's Underground
- North Dakota's Underground
- Ohio's Underground
- Oklahoma's Underground
- Oregon's Underground
- Pennsylvania's Underground
- South Carolina's Underground
- South Dakota's Underground
- Tennessee's Underground
- Texas's Underground
- Utah's Underground
- Vermont's Underground
- Virginia 's Underground
- Washington DC Underground
- Washington's Underground
- West Virginia's Underground
- Wisconsin's Underground
- Wyoming's Underground
- Off World Underground
- 1990: D.I.P. Project Marxen UFO88
- 1991: Underground Cities of Mars - Article
- 2015: Mars’ Photo Reveals Alien Ship, Underground Bunker and Other Structures
- Off Planet Underground Bases
- Was a Mysterious Underground Structure Found On the Moon?
- Pole Underground
- South American Underground
- Congo's Underground
- Egypt's Underground
- Kenya's Underground
- Sahara Desert's Underground
- South Africa's Underground
- Zimbabwe's Underground
- Afghanistan's Underground
- Cambodia's Underground
- China's Underground
- India's Underground
- Iran's Underground
- Israel's Underground
- Japan's Underground
- Kashmir's Underground
- Mongolia's Underground
- Russian Underground
- Saudi Arabia's Underground
- Tibet's Underground
- Turkey's Underground
- Vietnam's Underground
- Bahama's Underground
- Belize's Underground
- Costa Rica's Underground
- Guatemala's Underground
- Mexico's Underground
- Panama's Underground
- Puerto Rico's Underground
- Austria's Underground
- Crete's Underground
- Czechia's (Czechoslovakia's) Underground
- England's Underground
- Finland's Underground
- France's Underground
- Germany's Underground
- Iceland's Underground
- Ireland's Underground
- Italy's Underground
- Malta's Underground
- Norway's Underground
- Poland's Underground
- Romania's Underground
- Spain's Underground
- Sweden's Underground
- Wales's Underground
- Canadian Underground
- United States Underground
- Alabama's Underground
- Alaska's Underground
- Arizona's Underground
- Arkansas's Underground
- California's Underground A-J
- California's Underground K - N
- California's Underground O-Z
- Colorado's Underground
- Connecticut's Underground
- Delaware's Underground
- Florida's Underground
- Georgia's Underground
- Hawaii's Underground
- Idaho's Underground
- Illinois's Underground
- Indiana's Underground
- Iowa's Underground
- Kansas's Underground
- Kentucky's Underground
- Louisiana's Underground
- Maine's Underground
- Maryland's Underground
- Massachusetts's Underground
- Michigan's Underground
- Minnesota's Underground
- Mississippi's Underground
- Missouri's Underground
- Montana's Underground
- Nebraska's Underground
- Nevada's Underground
- New Hampshire's Underground
- New Jersey's Underground
- New Mexico's Underground
- New York's Underground
- North Carolina's Underground
- North Dakota's Underground
- Ohio's Underground
- Oklahoma's Underground
- Oregon's Underground
- Pennsylvania's Underground
- South Carolina's Underground
- South Dakota's Underground
- Tennessee's Underground
- Texas's Underground
- Utah's Underground
- Vermont's Underground
- Virginia 's Underground
- Washington DC Underground
- Washington's Underground
- West Virginia's Underground
- Wisconsin's Underground
- Wyoming's Underground
- 1990: D.I.P. Project Marxen UFO88
- 1991: Underground Cities of Mars - Article
- 2015: Mars’ Photo Reveals Alien Ship, Underground Bunker and Other Structures
- Off Planet Underground Bases
- Was a Mysterious Underground Structure Found On the Moon?