The now-abandoned tunnels were built for the transcontinental railroad on the route where the first wagon train entered California.

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

The world's oldest bookshop still in operation.

This abandoned five-star hotel is now a five-star urban exploration destination.

One of the largest Roman settlements in Portugal.

The medieval castle built as headquarters for the Pope's secretive Knights Templar.

Elaborately carved to showcase the glorious wealth that the age of exploration brought to the Portuguese empire.

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

An ancient and majestic fortress that played an integral role in Portugal's road to independence.

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

This unreal Portuguese palace looks as though it's made from a pile of different castles.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.