The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

A beautiful geyser under environmental threat.

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

Also known as the Blue Church, the building was consecrated to the daughter of Andrew II.

The largest fountain in Bratislava.

Thousands of slain Soviet soldiers are buried within the shadow of this enormous obelisk.

This Slovak bridge is known both for its connection to a national uprising and its UFO-shaped eatery.

This Slovakian statue of an emerging sewer worker might just be a bronze peeping tom.

Giant WWII fortresses that fired 8,000 rounds a minute, now home to thousands of pigeons.

The medieval center of the Islamic world was also once the seat of Saladin's sultanate.

This memorial to the victims of the Romanian Revolution of 1989 is often compared to a potato on a skewer.

Romania's triumphal arch looks out over Bucharest.

This communist behemoth is the heaviest building in the world and a legacy of a brutal regime.

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

In Egypt's expanding metro area, many of the neighbors are dead.

In the hinterlands of Serbia's capital, a giant reflective mushroom houses an aeronautical history of the former Yugoslav republic.

Destroyed Serbian army headquarters sits half crumbled in a largely revitalized Belgrade.

Sofia's legislative center is continuously reinventing itself.

"Holy Wisdom" overlooks the city that became its namesake.

A striking symbol of the Bulgarian capital.

A Bulgarian monument to Russia's role in World War II is constantly being painted in pop culture protest.

This building has two facades of clashing architectural designs.

A gorgeous mural outside a beloved D.C. restaurant pays homage to famous Black Americans.

The remnants of two World's Fairs are here, complete with a 12-story globe, a mini-Manhattan, and a UFO-shaped pavilion.