Cairo, Egypt
Nilometer
An ancient instrument used to measure the waters of the Nile so Egyptian farmers would know whether to expect famine or flood.
Places I want to go
Places on this traveler's wishlist.
Cairo, Egypt
An ancient instrument used to measure the waters of the Nile so Egyptian farmers would know whether to expect famine or flood.
Cairo, Egypt
A strange aquarium with stuffed fish, and almost no water for them to swim in.
Ballycastle, Northern Ireland
The lake that fills and empties itself at random.
Boawae, Indonesia
A real-life "hobbit" cave in Flores, Indonesia.
Moab, Utah
It's safe—and permitted—to walk across these twin natural sandstone arches.
Tamura, Japan
These wondrously illuminated caverns extend under the mountains of the Fukushima Prefecture.
Osimo, Italy
A series of caves, tunnels, and wells filled with fascinating figures and symbols.
Qesm Saint Katrin, Egypt
The deadliest diving spot in the world is also a stunning geological marvel.
London, England
This coffee shop lies hidden beneath a historic church.
Kaymaklı Belediyesi, Turkey
While not Turkey's deepest underground city, this subterranean redoubt is the largest.
Derinkuyu, Turkey
The deepest underground city in Turkey was designed to protect 20,000 people behind massive stone doors.
Tbilisi, Georgia
The secret room where early Bolsheviks cranked out propaganda fliers on a smuggled printing press.
East Jerusalem, Israel
Descend 2,030 years into the past in an ancient tunnel built to support Jerusalem's most famous wall.
García, Mexico
Inside this mountain lies several kilometers of breathtaking caves.
Ecuador
This cave system allegedly holds the "metallic library" of a lost ancient civilization.
Mirny, Russia
The world's second-largest excavated hole.
Georgia
Ancient rock-hewn town that witnessed key events of Georgian history.
Penteli, Greece
Hideout of thieves, monks, and goat-footed gods.
Verul, India
This complex of vertically-excavated Buddhist, Jain, and Hindu monolithic temples in India's Maharashtra providence illustrates a spirit of tolerance characteristic of ancient India.
Ethiopia
An ancient Ethiopian cave church is endangered by the simple building of a road.
Nagasaki, Japan
Once the most densely populated place in the world, this island is now a ghost town.
Banff, Alberta
The natural hot spring that was integral to the creation of Canada's first national park.
Stockholm, Sweden
This building, previously used as a courthouse, has an unusual geological feature in its basement.
Skarpnäcks Gård, Sweden
This hole formed by a glacier is the largest and best-preserved of its kind in Stockholm.