Perhaps the most spectacular grotto along the Algarve coastline.

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

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

A 16th century chapel decorated with bones, skulls, and entire bodies hanging from the wall.

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

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

Get up close and personal at this Fresnel Lens.

A sculpture made from recycled materials and hand-blown glass dedicated to transportation and transformation.

One man’s hobby is another man’s world of metal wonders.

The headquarters in Salem doubles as an occult art gallery.

Statue in Salem of the woman who starred as the witch Samantha in the sitcom "Bewitched."

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

Legend has it this spring formed at the spot where a medieval Swedish king was killed.

A large collection of ancient runestones decorates this university courtyard.

A prehistoric geological oddity tucked behind Stockholm's natural history museum.

The Swedish flag over this small naval fort signals that the nation is at peace.

Stockholm's narrowest alley is barely over two feet wide.

The discovery of an old wall led to the creation of this fascinating museum about the city in the Middle Ages.

An ancient Viking runestone hidden in plain view in Stockholm's old town.

Stockholm's deepest subway station is also a stunning ecological wonder.

It houses the remains of a 17th-century version of the Titanic.

An illuminated manuscript comprising the life's work of a lone monk, inexplicably decorated with a portrait of Satan himself.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.

Dine on food tied to Viking history and legend at this subterranean Stockholm spot.