Bacteria and algae give the salty water its bubblegum hue.

One of Madrid's oldest trees, with a long and colorful history, resides in El Retiro Park.

This fantastical faceless sculpture in Spain is on the grandest scale.

This 11th-century fortress is now the seat of Aragon’s state legislature.

Remains of the walls of the Roman city named for its founder

This amazing cathedral was built on the site of the first Marian shrine in Spain and is important to Spanish speakers the world over

An underground city of ancient quarry tunnels hid thousands of Allied soldiers in WWI.

A mosaic-tiled house built by graveyard sweeper Raymond Isidore.

The famous winding walk at Chartres is surrounded in mystery and myth.

Two very different statues celebrate the literary legacy of this medieval Dordogne town.

Beneath the city of Lourdes, France is a massive, concrete church.

The history of sea-faring refuse and disaster is on cramped display in this Netherlands folk museum.

Rich with fauna and flora, nature-lovers can walk across the sea at this UNESCO World Heritage spot.

A monument to a beloved aquatic folk hero in the Irish town of Dingle.

Ireland's only cable car once carried livestock across a treacherous strait.

An important landmark in the history of algebraic logic.

On the clock tower at St. Anne's Church in Cork, you never know which face is telling the truth.

One of the oldest lighthouses in the world, this structure was built more than 800 years ago.

Once the longest bridge in Ireland, this rusting span sits abandoned and overrun by nature.

A 300-year-old cottage decorated with tens of thousands of seashells arranged in intricate patterns.

A hugely vast Irish landscape of barren rock that stretches for miles.

This singular Irish dolmen is more Frank Lloyd Wright than upright stonehenge.

Unchanged for centuries, this medieval library keeps its books in chains.

A stunning gilt bronze relief denounced by Hitler as "degenerate art"—even though it was dedicated to the Nazi leader.