This remnant of an ancient Persian city is considered to be the world's largest single-span brick vault arch.

A roadway designed for a visiting monarch.

The second-largest natural arch in the Chartreuse Mountains.

Unscathed for almost 2,000 years, the best preserved Roman triumphal arch is in a small southern Italian city.

Tucked between a side street and a theater, this arch once led to a prestigious riding school, and now opens to a courtyard and community garden.

A triumphal steel arch on the side of a German mountain.

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

Three abandoned missile silos are hiding in plain sight behind a suburban development in Maryland.

A picturesque example of brute-force engineering conquering nature.