This abandoned five-star hotel is now a five-star urban exploration destination.

This colorful creation wasn't always a welcome part of Toronto's Moccasin Trail Park.

Aqueducts have dramatically changed this old lake, now home to tufa towers and its very own species of tiny brine shrimp.

Come for the speed, leave in love with the desert.

A sculpture for the sun and stars, created by Nancy Holt.

The Gaudí-inspired building that was the start of Terrassenc modernism.

This imposing modern citadel started out as a home renovation project.

A 16th-century horror show built in a lovely Italian garden.

This whimsical castle of grottoes was the labor of love of a French postman, and one of the greatest achievements of outsider architecture.

An art museum with an eclectic design and a scandalous past.

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

This singular art museum in São Paulo is unique inside and out.

This massive Brazilian church is built like an angular, technicolor pyramid left by Mayans from the future.

Giant eggs, walls of bread, and nightmare surreality mark the largest collection of works by Salvador Dalí.

A lush indoor jungle fills this bustling Madrid transportation hub.

A unrivaled and rather horrifying collection of wax dermatological models.

France's national museum of scientific and industrial instruments.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

Notorious artist squat renovated into legal studios.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

France's most famous cemetery, with some of its most curious tombs.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

These secluded and abandoned anti-aircraft defenses have become one the most scenic viewpoints in Barcelona.

The anatomical-pathological collection of a man who changed surgery.