A crew of die-hard train buffs spent decades turning a defunct stretch of railway in Oklahoma City into a museum now home to over 50 antique and restored trains.

The train collection of an eccentric New England seafood mogul is now a National Historical Site.

A huge railroad museum with over 100 pieces of rolling stock focusing on the railroad history of Pennsylvania.

Enormous crabs, bioluminescent jellies, and other amazing creatures from the ocean’s depths—some of which are in an aquarium for the first time ever.

An immersive environment that is part haunted house, part choose-your-own-adventure, and part jungle gym.

Walking around West Harlem reveals a scavenger hunt of beautiful bird murals.

A thorough look at the development and history of the underground's rolling stock of the Madrid subway system.

These ungulates have quite literally bounced back from the brink of extinction.

Head to the mountains to catch a glimpse of Spain's endangered subspecies of brown bear.

Holy Hindu shrine in an enormous, monkey-filled limestone cavern.

One of the largest caverns in the world has a maw large enough to stack cathedrals in.

These jagged limestone blades cut out through the canopy of the jungles of Borneo.

A wonderful collection of fossilized dinosaurs and other creatures that roamed the landscape millions of years ago.

Once close to extinction, there is no shortage of elephant seals on the beaches of Año Nuevo State Park.

This Arab fortress was once the largest citadel in Western Europe.

Peek into a cave of giant, glimmering crystals.

A memorial sculpture to heath hens stands on the spot where the last heath hen, Booming Ben, was last seen.

The statue honors the booming birds Rothsay, Minnesota, is famous for.

A memorial to a giant seabird that was hunted to extinction.

This five-foot-tall bronze bird is a memorial to a species that was hunted out of existence.

Thousands of bats stream out of caves every night on the edge on Thailand's second largest park.

This cavernous swimming spot doubles as a home to the largest known colony of bats in Central Asia.

Take a hidden path to the mouth of the cave to watch millions of bats swarm at sunset.

This breathtaking island on Rwanda’s Lake Kivu is a haven for thousands of fruit bats.