photo credits: instagram
Cappadocia is home to several underground cities, such as Derinkuyu and Kaymaklı, carved into the soft volcanic rock.
photo credits: instagram
This vast underground network of tunnels and chambers houses the remains of around six million people.
photo credits: instagram
A UNESCO World Heritage site, Wieliczka Salt Mine has been in operation since the 13th century.
photo credits: instagram
Used by the Viet Cong during the Vietnam War, the Cu Chi Tunnels near Ho Chi Minh City are an extensive network of underground passages.
photo credits: instagram
These interconnected cave systems are renowned for their stunning stalactite and stalagmite formations.
photo credits: instagram
Located beneath The Greenbrier, a luxury resort in West Virginia, this Cold War-era bunker was built as a secure location for the U.S.
photo credits: instagram
Each winter, the Icehotel in Jukkasjärvi is constructed using ice from the nearby Torne River.
photo credits: instagram
Located in Portland, Oregon, the Shanghai Tunnels are a network of underground passages with a mysterious history.
photo credits: instagram
It features beautiful mosaics and serves as a unique religious and historical site.