Beyond the obvious
Rome is the Roman ruin city, but the Empire stretched across Europe. Cities at the periphery — Trier (Gallia Belgica), Mérida (Hispania), Nîmes (Gallia Narbonensis), Pula (Histria) — sometimes have better-preserved monuments than Italy itself.
Rome
Rome the obvious capital. Colosseum, Roman Forum, Palatine Hill, Pantheon, Baths of Caracalla. Combined ticket €18 covers Forum + Colosseum but reservations now mandatory. Centro Storico walking-distance.
Athens
Athens Greek but layered with Roman — Roman Agora, Hadrian's Library, Tower of the Winds, Temple of Olympian Zeus. Combined ticket €30 covers all classical sites including Acropolis.
Trier
Trier Germany's oldest Roman city. Porta Nigra (best-preserved Roman gate north of Alps), Imperial Baths, Roman Bridge, Amphitheatre. Compact, walkable, free to walk past most. UNESCO World Heritage.
Nîmes
Maison Carrée (best-preserved Roman temple), Arena (still hosts bullfights), Pont du Gard aqueduct nearby. Small French city, day-trip from Avignon or Marseille.
Mérida
Spain's Roman capital. Theatre, Amphitheatre, Bridge over Guadiana, National Museum of Roman Art. €17 combined ticket. Day-trip from Sevilla (3h train).
Pula
Pula sixth-largest Roman amphitheatre in the world — better preserved than many in Italy. Temple of Augustus, Arch of the Sergii. Croatia coastal day-trip.
Strategy
Combined-ticket days save money everywhere. Book Colosseum 2+ months ahead. Smaller cities (Trier, Mérida, Pula) often free to walk past the major monuments.