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

A mecca for India's Jains.

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

The 953 windows undoubtedly make this the world's most beautiful screened porch.

The world's second-largest sundial, made entirely out of stone.

Sacred Indian temple that’s all monkey business.

This abandoned fort is said to be the most haunted place in India, so much so that entry is prohibited after sunset.

Thousands of exquisitely carved stone water storage wells, hundreds of stone steps fill this exquisite medieval stepwell.

A nearly unconquerable island-fort in the Indian Ocean.

Rock-cut cave complex filled with ancient Buddhist artwork.

Half-size replica of the Taj Mahal.

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.

Temples adorned with intricate, erotic sculptures make up one of the "seven wonders" of India.

The largest tiger reserve in India is a vast expanse dotted with ancient ruins of Nagarjuna Viswa Vidyalayam.

A centuries-old lookout post still sits atop a natural stone spire.

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

The second-longest continuous wall on the planet protects a hidden secret in the deserts of India.

This abandoned subway station beneath the Waldorf-Astoria hotel is allegedly used to secretly transport presidents.

The longest continuous lava tube in Oregon.

On the Oregon coast there is a natural hole that seems to be draining the sea.

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.

A collision of human error and natural geothermal pressure created this rainbow-colored geologic wonder.