A UNESCO World Heritage site, Hadrian’s Wall marked the border between Roman Britain and raiders and the unconquered peoples from the north (modern-day Scotland). Sections of this wall, which date to the second century, survive today. The wall was named after Emperor Hadrian and also featured forts up and down the wall. Fun fact: Hadrian’s Wall was the inspiration behind George R.R. Martin’s A Game of Thrones series. © Adfoto | Dreamstime.com

In Istanbul, Türkiye, you’ll find the Walls of Constantinople, built under Constantine the Great between the fourth and fifth centuries. The walls originally featured gates, with some, like the Golden Gate, restored. The Walls of Theodosius are another popular section of the walls. © Tolgaildun | Dreamstime.com

Yes, even London retains some fascinating Roman history. At Tower Hill, a statue of Emperor Trajan stands before a section of the London Wall. The statue is a cast of a late first-century statue found in Naples, Italy. The London Wall dates back to 200 when the city was known as Londinium. © PGregoryB | Dreamstime.com

Did you know there was another Roman wall built farther north of Hadrian’s Wall in England? The Antonine Wall was constructed between the Firth of Clude and the Firth of Forth in Scotland in the second century. Along the wall are some preserved forts, including Rough Castle Fort. The wall also featured the iconic Bridgeness Slab, a distance slab made to mark the completion of a section of the wall. It’s considered one of the best preserved of the Scottish distance slabs, and is on display at National Museum of Scotland in Edinburgh. © Colleen Ashley | Dreamstime.com

In Sofia, Bulgaria, the Romans conquered the city in 29 B.C.E., transforming the area into an important economic center. Remnants of the city’s Roman past survive today through walls, gates, churches and an amphitheater. Spot part of the Roman walls in the northeast corner of the old city. At Serdica Archaeological Complex, you’ll also see Roman streets, baths and an early Christian basilica. © Sergio Delle Vedove | Dreamstime.com

The Roman walls of Lugo, a UNESCO World Heritage site, stand in Lugo, Spain. These third-century structures also feature 10 gates, five of which date to Roman times (Porta Miña and Porta Falsa are the most iconic of them). Of the original towers on the wall, 49 are still intact, too. © David Andres Gutierrez | Dreamstime.com