At the height of alum production at this factory, human urine was a valued commodity.

The sole surviving medieval street cross in Scarborough.

80 years of the Battle of Peasholm on a small English lake.

Manchester's abandoned train depot lingers in a post-industrial purgatory.

This Polish cave has housed a dragon, a brothel, and an enduring legend.

An extraordinary "City of Caves" carved from solid stone.

A complex of six forts embedded in the Rajasthan hills.

The remains of what was, not so long ago, the world's largest city.

This complex of vertically-excavated Buddhist, Jain, and Hindu monolithic temples in India's Maharashtra providence illustrates a spirit of tolerance characteristic of ancient India.

Rock-cut cave complex filled with ancient Buddhist artwork.

More than half of this Indian palace is drowned but it looks all the more spectacular for it.

Machinery left over from California's once thriving mercury industry now attracts artists and explorers.

These Stalin-era industrial 'death traps' hang lifeless above the city

This ancient village and its adjoining cemetery have a beautiful history of death and remembrance.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

Rebuilt remains of a temple to Roman god Mithras.

The largest catacomb system in the world.

A 605-page Quran penned in the blood of a dictator is locked away in a mosque.

The anatomical-pathological collection of a man who changed surgery.

Dating back almost 400 years, the oldest public collection library in the United Kingdom was once the study hall of Karl Marx.

A 19th-century time capsule of travel, fiction, and historic texts still available to the public.

These lovely Turkish-styled baths were brought back to life after winning a reality show competition.

Despite having a dome made of papier-mâché this tiny observatory has survived for over a century.

Towns with a resource known as "white gold," valuable enough to fight a war over, now stand ghostly and empty.