The fifth-longest natural arch in the world, and the longest outside China.

This striking arch, one of the first architectural elements constructed in Prospect Park, was recently restored to its original glory.

It's safe—and permitted—to walk across these twin natural sandstone arches.

When new viceroys were elected, they passed through this arch to cement the title.

The first neighborhood to implement the Garden City model in its suburban planning.

The Byzantine, pre-Columbian, and medieval art at this stately mansion are some of the most under-appreciated collections in D.C.

Designed by Maya Lin, the memorial honors 41 individuals who died fighting for equal rights between 1954 and 1968.

This memorial honors thousands of enslaved Africans and their descendants who died in colonial New York.

The unbelievably opulent home built for an infamous newspaperman.

In the mountains of West Virginia is this perfectly preserved Art Deco train station.

Constructed by forced laborers, this submarine pen is now a museum and war memorial.

Life-size figures portray depot attendants, train crew, and passengers frozen in time at the oldest railroad station in Arkansas.

An abandoned Ecuadorian prison that once held ex-presidents and notorious con artists is now a carceral museum.

Harry Potter’s Hogsmeade Station is also a charming blast from the past situated in North Yorkshire.

After this former brothel closed, its interior remained almost frozen in time.

A cheeky architectural easter egg.

A glorious pub known for a spiteful printing feud and its famous typeface lost—then found—at the bottom of the Thames.

A giant bronze coil of feces is both a tribute to doggie defecation and a reminder to pick it up.

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

In the basement of the U.S. Capitol Building is a hidden storage room full of ornate floor tiles leftover from the 1850s.

An 18-mile-long tunnel for sewage waste will soon wind within the bowels of Washington, D.C.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

Obscure Freemasons still live in D.C.’s largest private residence.

Despite many attempts to finish this overpass, it has been abandoned since the 1970s.