Rome becomes easier when ancient sites, central squares and Vatican-side plans are separated into logical days.
Day 1: Colosseum and ancient Rome
Focus the first day around the Colosseum and Forum area.
Day 2: historic center
Use the second day for Trevi, Pantheon and central piazzas.
Day 3: Vatican side and slower neighborhoods
Reserve the final day for Vatican-related plans and nearby areas.
Leave time for meals and walking
Rome rewards slower transitions between major sights.