Thanks to modern navigational tools we now know that the true prime meridian runs through a park next door.

One of the world's largest collections of pathological specimens.

This wildly-tiled artist's palace is a living and growing account of the creator's life, loves, and labors.

One part local history, 99 parts gruesome haunted house.

The largest of London's subterranean rivers and once a mad, bad center of London life.

An unusual round church in London with a Templar past.

This collection of illusory paraphernalia has been culled from the history of London's premier magician's club.

This South London cemetery holds the remains of more than 15,000 people.

A kaleidoscopic warehouse-maze of handmade neon signs.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

The walls of Germany's Parliament still show the scars of the Red Army takeover in World War II.

Berlin's old airport.

An abandoned NSA listening post on Berlin's "Devil's Mountain."

A state-of-the-art medical facility from the Imperial era is now a derelict ruin.

A collection of abandoned typographic signs from Berlin and beyond.

The most visited, and possibly most controversial, museum in Germany.

A space dedicated to contemporary art and culture, co-chaired by fashion icon Miuccia Prada.

The secret medieval communication system will whisk your words above the noise of the crowd.

An exclusive waiting room built for the royal family in the 1920s is hidden in Milan’s central station.

Long-abandoned art nouveau baths beneath Milan's Piazza Oberdan.

The oldest botanical garden in the world that technically isn't the oldest.

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

The world's oldest surviving anatomical theater, where "the dead are pleased to help the living."

This abandoned island off the Venetian coast has been a radical monastery, a political prison, and a secret Nazi base.