Hidden in a grotto 26 feet below Nottingham's oldest hotel, this stylish subterranean drinking den is notoriously hard to find.

This giant urban staircase was built to keep the city's brave fighting men from getting waylaid in the red light district.

Ancient man-made caves underneath small town Belgium.

Part modern art project, part traditional chapel, this see-through church is only substantial from the right angle.

Hiding the longest subterranean river known in the world.

Descend into the tunnels to experience the life of a coal miner.

This abandoned Belgian fortress is purposefully being left to nature.

Sculpture designed by Turkish artist and professor Mehmet Ali Uysal.

A beautiful maze marks where three countries meet.

This centuries-old gothic monster has been converted into a sprawling, glossy bookstore.

Pull up and have a drink at a museum filled with hundreds of years worth of shipwreck artifacts.

This small town in the Netherlands has no roads but instead, miles of canals and over 100 bridges.

Inspired by "The Starry Night" this Dutch bike path turns into a glowing work of art each night.

A Netherlands hotel where you can sleep inside a wine barrel.

Go inside a revolutionary, cage-less zoo where 70 species of monkeys roam free alongside their human visitors.

Peek through a transparent pyramid and drink in the mountain made of books.

Survival capsules find a second life as a unique hotel.

The works of poetry's biggest names grace the walls of the city of Leiden, all carefully painted by hand.

A historic observatory now an astronomy museum beautifully situated at the moat of the Middle Age city centre.

This ghost town in Belgium will lose its street art when it ceases to exist.

Colorful and chaotic stacked hotel in North Holland.

The spectacular history of spectacles on display.

A beautifully eclectic mix of architectural styles.

An Amsterdam street lined with antique shops each one dedicated to a different obscure collection.