A hilltop town, Langres was built on a limestone promontory of the same name. This stronghold was originally occupied by the Lingones. At a later date the Romans fortified the town, which they called Andemantunum, located at a strategic crossroads of twelve Roman roads. The first-century Triumphal Gate and the many artefacts exhibited in the museums are remnants of the town's Gallo-Roman history. After the period of invasions, the town prospered in the Middle Ages, due in part to the growing political influence of its bishops. The diocese covered Champagne, the Duchy of Burgundy, and Franche-Comté, and the bishops obtained the right to coin money in the ninth century and to name the military governor of the city in 927. The Bishop of Langres was a duke and peer of France. The troubled 14th and 15th centuries caused the town to strengthen its defenses, which still give the old city its fortified character, and Langres entered a period of royal tutelage. The Renaissance, which returned prosperity to the town, saw the construction of numerous fine civil, religious and military buildings that still stand today. In the 19th century, a "Vauban" citadel was added.
Langres has a historic town center surrounded by defensive walls with a dozen towers and seven gates.
A museum called the Denis Diderot House of Enlightenment opened in 2013. This museum, set up in a private mansion from the 16th and 18th centuries, is dedicated to the philosopher Denis Diderot .