A nuclear reactor created for Eisenhower's "Atoms for Peace" campaign is now used for research at a Dutch university.

An early 19th-century English style garden hidden in the Rotterdam cityscape.

A subterranean relic of the Spanish Civil War hides below this picturesque park.

Stuck in the middle of a modern Madrid city block are the remains of a 19th century sports complex.

This funky former tobacco factory is one of the most striking examples of Madrid's cultural diversity.

This wooden recreation of a 9th century lake village looks as though it was built yesterday (which it relatively was).

Latvia's symbolic mountain-shaped national library is home to millions of cultural tomes.

The oldest housing complex in Riga is a mini timeline of architectural trends.

An enormous roadside attraction in the heart of Spain's toy-making hub.

These "mermaids" that surround a plaza in Segovia are rather sphinx-like.

A surrealist labyrinth and museum of contemporary sculptures.

The last of three massive blast furnaces that were once at the foundation of the Port of Sagunto economy.

The legendary bathing site of a Moorish queen is actually part of a Roman fish farm.

This exhibition space designed to look like the skeleton of a whale is hidden underground.

A 12th century church completely covered in shells.

The ruins of an ancient Celtiberian town with incredible rock-cut buildings and a Roman aqueduct.

Walls of stone rise up from sinkholes caused by underwater erosion.

Haunting monument to the German Jewish philosopher who died while fleeing fascism.

This stop on the Camino de Santiago stands high above the underwater ruins of a medieval town.

The ruins of a bombed medieval village memorialize the destruction of the Spanish Civil War.

A whimsical garden of outsider art in the Spanish countryside.

Vibrant street art created with mixed media.

This enchanting hamlet carved into the rock looks like something straight out of Tolkien's Rivendell.

Considered the birthplace of the Copper Age and Bronze Age, the river is tinted red from 5,000 years of mining.