This collection of historical artifacts and tropical wildlife waits just beneath the surface of the water.

Tropical paradise strewn with hundreds of World War II wrecks.

An isolated dive site teeming with cnidarians.

Canada's oldest railway tunnel is illuminated in a rainbow of color as it passes under the streets of this small city.

An outlandish shoe shaped house built by an eccentric millionaire.

This bug-eyed water wheel uses the power of the Sun to clean up Baltimore Harbor.

This historic lighthouse was well known for the large number of women who served as its keeper.

This statue of two men in a rowboat was erected to honor those who died while fishing in the Chesapeake Bay.

Once the supplier for noteworthy projects like the National Cathedral, this old brickworks now lies abandoned.

An Industrial Revolution-era public work that purified water using nothing but sand.

Live data is transmitted from the Atlantic coast to instantly recreate the ocean waves in this fountain at the NOAA headquarters.

Giant acorn-shaped 19th century gazebo from which suburban Washingtonians gazed upon the original "silver" spring.

A tribute to the pop culture icon overlooks this Washington D.C. intersection.

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

Before Metro, Washington had a robust streetcar network—and you see the remains of this infrastructure if you know where to look.

The hidden offices underneath Memorial Bridge have been locked up since 1976.

Please don’t anchor your boat onto the Department of Defense’s underwater data cables.

The system of air guns are fired off remotely to scare any trespassing avians.

The remains of a historic plantation nestled in between a parking lot and the rental car return at Reagan National Airport.

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

This isn't your average roadway—it's actually a National Park and a transportation pioneer.

A lawn full of retired spacecraft on display at one of NASA's first research labs.

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

At Washington's Dulles Airport is a satellite museum (no pun intended) with three quarters of a million square feet of aircraft history.