Tunnels

A century-old network of freight tunnels underneath the city's historic business district.

One of the most breathtaking railways in Europe also takes one of the steepest climbs, from fjord to mountain plateau.

Descend 2,030 years into the past in an ancient tunnel built to support Jerusalem's most famous wall.

The beautiful tunnel that ran from the lobby to Penn Station is still hidden underneath 34th Street.

A 500-year-old series of tunnels long believed to be folkloric was uncovered beneath the streets of Puebla.

The tunnel's elegant proportions keep you snug with no claustrophobia freak-out.

This frozen tunnel in central Alaska is both an engineering feat and a valuable climate classroom.

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

A centuries-old complex of hand-dug stone chambers has sheltered locals in times of trouble.

The first tunnel to be dug beneath a river, repurposed as an art and museum space.

A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

This hidden stream beneath Indianapolis makes an appearance in the best-selling novel "Underground Airlines."

Underground tunnels once home to crime are now back open to the public.