World's first "penitentiary," meant to be humane, drove men insane.

This museum offers a journey back to the Belle Epoque era of Romania.

A chemical factory damaged by two earthquakes and an explosion that became abandoned after bankruptcy.

An abandoned pasta factory in the centre of Bucharest, once home to Bulgarian revolutionaries and a hub of crime.

A Romanian church built from one single oak.

One of the oldest churches in Romania is believed to have been built on the site of a pagan temple.

A giant portrait of an ancient king looms over the river.

A small town Romanian cemetery filled with darkly humorous gravestones.

This elaborately decorated, fairytale-like Romanian royal palace is one of the most striking castles in Europe.

The possible imprisonment of Vlad the Impaler here earned the medieval castle its nickname, "Dracula's Castle."

Some call this eerie forest of crooked trees the "Bermuda Triangle of Romania."

Moss and stone turn this waterfall into an otherworldly liquid veil.

This fairy-tale castle would make Dracula (who is said to have been imprisoned there) jealous.

A cluttered and astounding collection of antiquities and curiosities.

Remnants of a Victorian garden feature sitting in public woodland.

The world's first underground farm is in a World War II bomb shelter beneath the streets of London.

A subterranean ice warehouse that has lain hidden beneath central London for over a century is now open to the public.

A memorial to a dog that inspired rioting in the streets of London.

Buried for centuries, this hidden cellar is all that remains of London's medieval Whitefriars Monastery.

At almost 1,000 years old, this is the oldest known door in all of Britain.

Hidden beneath the streets of London is a secret subway that only carried mail.

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

This shop and gallery is a modern-day cabinet of curiosities, unassumingly positioned along an urban thoroughfare.

Check out engineering marvels of the past at this unintentionally retrofuturist museum.