The theatre
Tiers for four thousand still used for summer performances — climb to the top row for the view.
Livioandronico2013 — CC BY-SA 3.0 · Public domain · MatthiasKabel — CC BY-SA 3.0 · Sonse — CC BY 2.0
The Roman theatre is the heart of Ostia Antica: Rome's ancient port and a complete preserved city half an hour from the capital. Agrippa built it under Augustus and Commodus enlarged it to hold four thousand; it is still used for summer performances — you sit on the same steps the Romans sat on. Directly behind it lies the Square of the Guilds: a courtyard ringed by the offices of shipping firms from across the Mediterranean, each fronted by a floor mosaic advertising its trade — ships, fish, elephants, and the names of cities in Egypt, Tunisia and Syria. It is as close as anything gets to a Roman business directory preserved in the ground. And Ostia as a whole deserves the day: paved streets, apartment blocks several storeys high, baths with complete mosaics, bakeries with their ovens, public latrines, temples. Far less crowded than Pompeii and far easier to reach — a train from Piramide on an ordinary metro ticket. Take water, a hat and comfortable shoes: the site is vast and there is little shade.
Tiers for four thousand still used for summer performances — climb to the top row for the view.
A floor mosaic outside each shipping office naming its trade and home city — a living Roman commercial register.
Baths with complete mosaics, bakeries with ovens and millstones — daily life rather than palaces.
Multi-storey buildings with their stairs and flats — how ordinary Romans actually lived.
Viale dei Romagnoli 717, Ostia Antica
Ostia, without hesitation. Pompeii means three hours of travel each way and an exhausting full day; Ostia is half an hour on a metro ticket and gives you the same everyday Roman city with far fewer crowds. Pompeii deserves its own trip to Naples, not a day trip from Rome.
Yes — open space to run in, a theatre to climb, whole streets to imagine. But bring plenty of water and avoid midday in July and August.