Soldiers from “C” Company, Task Force 2-6 Infantry, take in the Arch of Ctesiphon, one of the largest and oldest free-standing arches in the world. Located in Salman Pak and constructed in 400 A.D., it is the only remaining structure of the city Ctesiphon, the largest city in the world during the sixth century. (Ben Bloker / S&S)

SALMAN PAK, Iraq — When the soldiers of Task Force 2-6 Infantry patrol through the market places of downtown Salman Pak, a city 15 miles southeast of Baghdad, they operate under the shadow of one of the world’s great landmarks.

At the edge of town stands the Arch of Ctesiphon, which is reported to be the world’s oldest free-standing arch.

Constructed in 400, it is the only remaining structure of the city of Ctesiphon, which was the largest city in the world during the sixth century. The city also was mentioned in the biblical Book of Ezra under the name Casphia.

On a recent patrol of downtown, the 2-6 soldiers made a stop at the site, which is guarded by members of the Iraqi army.

At one time, the city of Salman Pak was a tourist hub for Baghdad’s elite, with the arch serving as a top attraction. After years of violence and conflict it remains to be seen whether the city will again serve as a weekend getaway spot.

See more photos of the arch and Salman Pak here.