An unconventional and naturalistic sculpture depicting the artist marking his territory on an exterior faculty wall.

Built in 1981 in collaboration with Andy Warhol, this giant piece of pop art stands on the campus of Colorado State University.

It's believed that the dead were once taken out of houses through these now walled-up doors.

A floating cat sanctuary on an Amsterdam canal.

This ruined castle is said to be the legendary keep of a Viking princess.

The construction of a tram line unveiled hidden remnants of the old medieval city.

Artist's eccentric property excessively decorated with found objects and work of his own.

Grand architectural relics gain a new life in this Pennsylvania warehouse.

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

This small and often-overlooked museum holds some of Spain's finest artistic treasures.

Earth's rocky history has rarely glittered so brightly as it does in this Spanish museum.

Impossibly life-like natural history models created out of glass by a father and son.

The thousands of shades on display — some toxic, others impossibly rare — are a library of more than just color.

Museum dedicated to awful artwork.

Tens of thousands of tiny bottles stuffed with various items.

This house's itty bitty size means no humans allowed.

The largest medieval water tank on the Iberian Peninsula is preserved beneath the Cáceres Museum.

A neighborhood park in the city of Cáceres hides what some believe are revolutionary examples of Neanderthal cave art.

A lush indoor jungle fills this bustling Madrid transportation hub.

This fascinating and poignant museum chronicles every imaginable aspect of Spanish colonialism in the Americas.

A plaque in Madrid’s West Park marks the launch of a queer icon’s unlikely media career.

Order cookies baked by cloistered nuns in a 400-year-old monastery.

The little church's beautifully frescoed ceiling has earned it the nickname “the Sistine Chapel of Madrid.”

Sometimes called the Banksy of Madrid, Muelle was a pioneer of street art in the Spanish city.