The verdant mossy ruins of a Franciscan monastery lie in the remote Sintra hills awaiting exploration.

An early work of the architect Álvaro Siza Vieira, these swimming pools blend into the beach.

A garden in Lisbon filled with giant porcelain creatures.

A stunning 18th-century site where pilgrims ascend by a series of punishing stairs only to return via funicular.

This restored Portuguese cafe may well be the most beautiful place in the world to grab a Big Mac.

This gaping hole in the middle of a remote mountain lake looks like a portal to another dimension.

Picturesque intersection of witchcraft and ancient Christianity.

A unique seaside cave where Aleister Crowley faked his own death.

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

The stunning interior of this Gothic church is covered in ornate gold details.

A submerged village appears when dam levels drop.

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

One of the most beautiful bookstores in the world hides a neo-Gothic interior behind an art nouveau facade.

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

The world’s highest ski resort was deserted after an 18,000-year-old glacier melted away.

This medieval sanctuary's tree-framed door looks like a portal to a mythical realm.

One of New York's best collections of pinball is hidden in a secret bar in the back of this laundromat.

A monument to the military service of America's greatest traitor refuses to even name him.

A winding, cliffside stretch of road overlooking the Delaware River.

Large-scale contemporary artworks tower over fields and lurk in forests around a Jacobean manor house.

One of the largest sculpture collections in the U.K. features history's greats, from Bob Dylan to Galileo, in bronze.

This former quarry is now a vibrant labyrinth of magical in situ sculptures.

Hidden in plain sight, this creepy sculpture watches from above.

This silent sentry in the crypt below a large Gothic cathedral is often knee-deep in water.