The largest clock face in the United States is twice the size of Big Ben and infinitely more ad-sponsored.

A model of a dinosaur that was named for Andrew Carnegie stands outside the museum that also bears his name.

A restored Pittsburgh house of God has been converted to a marvelous house of suds.

Sections of the iconic limestone columns have been left uncleaned as a reminder of the city's polluted past.

The site where Poe "in great distress, and ... in need of immediate assistance" likely died.

The trials and tribulations of marking Poe's grave.

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

A girls' boarding school inspired by the Chicago World's Fair, once abandoned, now restored to strange and scenic glory.

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

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

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

A super-sized promotional trick that is now a D.C. landmark.

Largest Roman Catholic church in North America.

The most accurate timepiece in the world.

This lovely picnic spot featuring thunderous jet landings is an aircraft spotter’s dream.

At 207 feet, one of the world's longest continuous escalators.

The site of the climactic scene from the classic horror film is now a historic landmark.

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

A historic neighborhood church is reborn as a psychedelic arts collective.

This imposing Masonic temple a mile from the White House was the first public library in Washington, D.C.

This mysterious structure by the Washington Monument is a flood barrier designed to protect the White House against rising waters.

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

A bas relief commemorates the "Nuns of the Battlefield" who cared for soldiers on both sides of the conflict.

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