Rome is unusual among great cities in that its historic centre is genuinely compact. The walk from the Colosseum to the Vatican takes about an hour, and you pass most of what you came to see on the way. The layering is the point: a baroque church built over a medieval basilica built over a Roman temple is ordinary here rather than remarkable. Two practical realities shape any visit. The first is heat - July and August in Rome regularly exceed thirty-five degrees, and the ancient sites offer almost no shade. The second is queuing: the Colosseum, the Vatican Museums and the Borghese Gallery all require advance booking, and the Borghese caps visitor numbers strictly by timed slot. Water is free and everywhere; the city's nasoni fountains run continuously with cold drinking water, and carrying a bottle is more useful than any other single piece of advice.
When to visit
April, May, September and October. Avoid mid-August, when the heat peaks and much of the city closes.