Rome and Florence are the two anchors of an Italian trip — one the seat of an empire and the Catholic Church, the other the birthplace of the Renaissance. Only ninety minutes apart by train, they're often paired, but they reward very different amounts of time.
Rome operates on an imperial scale: the Colosseum, the Roman Forum, and Palatine Hill form a continuous archaeological zone you can spend a full day inside. Florence has nothing to match this — its history starts later, with the Piazza della Signoria and Palazzo Vecchio as its civic core rather than ancient ruins. If ancient Rome is what draws you, Florence won't compete.
Florence is the tighter, denser art city: the Uffizi Gallery, Accademia Gallery, and Pitti Palace & Palatine Gallery hold an outsized share of Renaissance masterpieces within a short walk of each other. Rome's Vatican Museums & Sistine Chapel and Borghese Gallery are individually just as spectacular, but they're spread across a much larger city and require more planning around lines and location.
Rome's St. Peter's Basilica is the center of global Catholicism and unmatched in sheer scale, while the Pantheon and Trevi Fountain add layers of pagan and Baroque grandeur nearby. Florence's Florence Cathedral and Basilica di Santa Croce are remarkable in their own right — especially the Duomo's dome — but read as civic pride rather than global religious weight.
Rome is sprawling and chaotic, best explored through neighborhoods like Trastevere and squares like Piazza Navona. Florence is compact and walkable, centered around Piazza del Duomo and the Ponte Vecchio, and makes an easy base for day trips — Siena chief among them, something Rome's day-trip options don't rival for Tuscan hill-town charm.
Choose Rome for ancient history on an imperial scale, the Vatican, and big, chaotic city energy. Choose Florence for the densest concentration of Renaissance art anywhere and easy access to Tuscany. With a week, most travelers do both — three or four days in Rome, two or three in Florence.