Troyes was founded by the Romans in the C1st A.D. The town remained relatively small until the early Middle Ages, and the rise of Champagne.
In the C12th and C13th, the Counts of Champagne gave their prosperous capital a series of fortifications. These were all demolished in the C19th and replaced by the present boulevards. Look at the map, and you will see that they form the outline of a ... champagne cork