Underground tunnels are made for different purposes like sewage system, to support foundation of structures and for other maintenance purposes. Thanks to a group of urban explorers who found out these architectural marvels which were beneath the street’s and cities of the world hidden from the reach of people.

1. Urban Design
10 Scariest Underground Tunnels
(http://smoont.com/10-scariest-underground-tunnels/)
Underground tunnels are made for different purposes like sewage
system, to support foundation of structures and for other maintenance
purposes. Thanks to a group of urban explorers who found out these
architectural marvels which were beneath the street’s and cities of the
world hidden from the reach of people.