A marvel of Byzantine engineering under the streets of Istanbul.

Live a night as a Byzantine King, with a minibar and private jacuzzi.

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

These tombs were built into the side of a mountain so that ancient angels could reach the dead.

A deadly ancient portal to the underworld.

Step back in time and witness the fall of Constantinople.

A small island less than half a mile from Venice is a forbidden island with a dark and twisted past.

Go inside to really appreciate this 500-year-old technological masterpiece.

Macabre astrological automaton clock dating to the late 1400s.

When the rain falls, this drain system turns into a musical instrument.

A unique hanging cable-car navigates through Dresden, the oldest suspension railway in the world.

Ruins of a German Castle on top of a towering stone pillar.

Underneath this small church are 15,000 bones, arranged by an obsessive academic.

A museum of alchemy and a basement laboratory all housed in an ancient building in a Gothic tower.

Microscopic scenes; some call it novelty, some call it art.

A perfectly running 230-year-old silver automaton and music box.

Museum preserving torture methods from the past.

Numberless clock creates a meal of time for the dreaded, insectile Chronophage.

Traveling collection of amazing automata.

A 200-year-old prison that now houses a peculiar crime museum.

The mysterious, fantastical woodland inspiration for "The Lord of the Rings."

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

A church of bones, decorated with 40,000 human skeletons.

Over 3km of caverns and caves at the Switzerland-France border contain the largest underground river in Central Europe.