Founded under Emperor Augustus in 17 BC near the tribal sanctuary of the Celtic Treveri, the city was an important administrative seat and emperor's residency in the late Roman period. For this reason, the epoch is represented here more strongly than elsewhere in Germany. Here you can experience the era authentically: Porta Nigra, the amphitheatre, the imperial baths, the Barbara Baths, the imperial throne room, the Roman bridge, the Igel Column, and the Trier Cathedral and the Church of Our Lady are all part of the UNESCO World Heritage site, and are within walking distance of the city centre.
It is sometimes hard to imagine that Trier was once one of Rome's greatest cities. Today, it is beautiful but unassuming. Two millennia ago, it became the capital of the Western Roman Empire and was used by Emperor Constantine as a base. It was his influence that cemented the spread of Christianity across Europe and the testaments to his faith make up some of the most important buildings in the city today.
In addition to the Roman period, Trier has a charming city centre: an extensive pedestrian zone with an enchanting historical backdrop and main market—the busy and lively heart of the city all year round. The Market Cross stands from the year 958 and is not far from the Petrusbrunnen (Saint Peter's Fountain) dating back to 1595. At the Market you can find the impressive 'Steipe', a 15th-century wine house with Gothic arches. Opposite, you can discover the oldest pharmacy in Germany, the Löwenapotheke, dating from 1241. And if it's living history you're after, Trier opens its streets to visitors through its medieval residences: half-timbered houses from the Renaissance, electoral buildings, and Karl Marx's birthplace.
According to visitworldheritage.com