A pedestrian island in the middle of world-famous Times Square emits a strange (and purposeful) humming noise.

A crumbling hospital from the 1850s on Roosevelt Island.

An enigmatic mural hiding in plain sight in one of São Paulo's busiest metro stations.

This neo-Gothic monastery offers a rare chance to witness the unique maned wolf right up close.

This Arizona observatory is famous for investigations into Martian life, and as the place humans first spotted Pluto.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

These free-roaming horses were once destined to disappear from the land.

Flames have been burning within this mountain for more than 2,500 years.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

America's only nuclear missile silo open to the public.