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

A curious collection dedicated to human and animal anatomy and pathology.

This city square is home to Amsterdam's oldest church and a statue honoring Dutch sex workers.

The most confusing clock in New York.

One of the Seven Wonders of the Modern World holds the world's tallest metal staircase.

One of the largest underground systems runs under Canada's largest urban center.

Op-art architecture designed for happiness.

A beautiful but toxic fountain of mercury.

In this historic region, homes and churches are carved into ancient volcanic rock formations.

The ancient latrines of the Greeks, in all their public glory.

Roman ruins top white travertine terraces formed by ancient hot springs.

This famous city eluded concrete detection until the early 2000's.

Turkish adventurer antiques in the heart of the Grand Bazaar.

A marvel of Byzantine engineering under the streets of Istanbul.

Breathtaking and huge 430 year old maps of Italy.

The mark of the Devil's horns on a marble column in Milan.

Small on the outside, big on the inside, this church is an astonishing act of visual deception.

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

The "dragon babies" of southeastern Europe.

A miniature train-ride through Slovenia's largest cave system.

One of the largest caves in the world open to the public.

Pilgrimage site for star-crossed lovers.

A complex, nine-layer maze on the grounds of a Venetian doge's playground.

Built to repay the sins of the father, this church is home to one of the most valuable works of Western art.