This ancient Hawaiian henge may have been an early star chart.

Hide from the tourist hordes in these relatively unknown, and unguarded lava caves.

Earth's tallest volcano is sacred to Native Hawaiians, and home to a dozen world-class observatories.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

Just below the surface, shrimp are producing temperatures hotter than the sun.

Rare recess caves fill this unbelievably beautiful Ohio park.

Take shelter from Hawai'i's tropical heat under the massive canopy of largest Banyan tree on the island.

The air force base preserves its scars from the Japanese attack on Pearl Harbor.

A bronze monument to the infamous radio broadcast in the real New Jersey town where the fictional Martians crash-landed.

Could it have picked a better place to land?

This unassuming home was once “grand central station” for the Underground Railroad.

Was there a small "backpack nuke" hidden in the attic? JFK apparently thought so.

A haunting exhibit in a wildlife refuge center highlights threatened species and the conservation efforts needed to save them.

Take a drunken tour inside the world's largest known geode.

This NASA test station is home to some of the world’s largest and most powerful space environment simulation facilities.

The world's tallest doric column is this Ohio monument to a naval victory in the War of 1812.

Deep scars on the earth left by the Ice Age.

Look closely and you’ll notice that the color changes a third of the way up the tower.

The semi-reclaimed ruins of this canal were once part of an ambitious plan to reroute the mighty potomac.

The romance of early commercial flight still fills this Art Deco destination.

These unusual rooms on wheels are holdovers from the 1960s.

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

A former major munitions plant that has been converted into a sprawling art space.

You can walk through the first Boeing Air Force One, which famously carried JFK's casket from Dallas back to D.C.