A well-preserved network of cavernous tunnels have spent silent centuries removing Toronto's waste.

One of the largest caves in the world open to the public.

One person's lost luggage is another person's treasure.

Crystal clear lake with a shoreline of travertine located in a Colorado canyon.

Dim sum, served in a grand old theater.

Extraordinary rock formations in open Peruvian fields.

Once a bustling fishing port, this semi-ghost town is now more than 90 miles away from the shore.

At the foot of a waterfall lies a peaceful swimming lagoon and evidence of over 60,000 years of human habitation.

Architectureal fantasy quarter of Rome.

A house and yard adorned with bizarre concrete sculptures in a Milwaukee suburb.

Enormous lake at the bottom of a unique cave system.

This notorious Canadian mental institution was home to some of the first LSD experiments and origin of the word "psychedelic."

The Gaudí-inspired building that was the start of Terrassenc modernism.

An explosion of natural color known as "the river that ran away from paradise."

The world's largest bioluminescent area was undiscovered by science until 2005.

An urban laboratory.

Museum dedicated to the preservation of surf culture.

Home to the largest urban bat colony in North America, estimated at 1.5 million bats.

The seamy, underground secrets of Portland's criminal past.

The world's highest and most dangerous infinity pool lies at the precipice of Victoria Falls.

A stunning, abandoned limestone quarry in southern Indiana provided the stone to erect the Empire State Building.

A beautiful but toxic fountain of mercury.

Monasteries on rock pillars, once accessible only by frayed ropes.

In memory of The Blur Building, the temporary exhibition pavilion of vaporous nothingness.