Slum Settlement Filled With Mountains of Garbage.

Standing atop 2nd-century Roman ruins, this church is one of the oldest and most iconic in Old Cairo.

The massive cave church of Cairo's Zabbaleen community is one of the largest Christian churches in the Middle East.

This ancient structure is widely thought to be the oldest intact pyramid in the world.

A hiking/biking/exploring trail that winds across over 140 miles of Rwandan shoreline.

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

This center in the Rwandan capital supports women’s livelihoods while educating visitors about traditional cooking, craft making, and more.

On the Fourth of July this area will transform into a Pompeii-like storm of falling embers and ash.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

One critic described it as "middle Mussolini, early Ramses, and late Neiman-Marcus." Another called it an architectural "natural disaster."

Corn-inthian columns with a uniquely American take on neoclassical architecture.

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

An overlooked memorial honoring the local Washington residents who died in World War I.

The little-known, 300-year history of the area includes former lives as a bustling tobacco port, parking lot, and industrial dump.

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

Legend has it that President Grant’s frequent drinking in the lobby gave rise to the term “lobbyist.”

Washington's iconic carousel has a nice piece of Civil Rights history.

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

Largest Roman Catholic church in North America.

The oldest continuously operating fish market in the United States.

The national park was once a plantation estate.

The walls of the iconic dome are hollow and have a secret stairway.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

Home to items never before seen by the public.