Trier
Trier on the Moselle, near the Luxembourg border, is one of Germany's oldest cities. Augustus founded it no later than 16 BC as Augusta Treverorum, and in late antiquity, it was one of the Roman Empire's capitals. Nowhere north of the Alps are so many Roman structures preserved.Nine monuments, including Porta Nigra, Imperial Baths, Amphitheater, Basilica of Constantine, Cathedral, and Church of Our Lady, have formed a UNESCO World Heritage site since 1986. Other attractions include the Main Market with its burgher houses and Karl Marx's birthplace. The city, with around 112,000 inhabitants, is compact; most sights are reachable on foot from the central station.