Take a prebooked airport transfer or official taxi to Hotel Pantheon near the Pantheon; taxis to the historic center are a fixed fare and drop you at the hotel door.
Go into the hotel, leave luggage at reception and request to store bags until official check-in at 14:00; this lets you start exploring light and secure.
Walk a few steps to the Pantheon to admire the ancient rotunda and oculus—entry is inexpensive or donation-based and the building opens typically in the morning (check day-specific hours).
Eat a budget-friendly lunch close to the Pantheon — Enoteca Corsi offers good value dishes near the square, or grab a panino for a lighter, cheaper option.
Walk or take a short taxi to the archaeological area for an exterior visit and optional entry to the Colosseum; the Forum and Colosseum typically open mid-morning to dusk—prebook Colosseum tickets if you want interior access.
Cross the Tiber to Trastevere for lively, reasonably priced eateries—Pizzeria Ai Marmi is a popular budget choice; reservations are useful but not always possible.
Walk back along the Tiber to Castel Sant'Angelo and the scenic riverside—walking is free and relaxing; the castle has a modest entry fee if you wish to go inside.
Explore Pompeii's ruins (the site typically opens in the morning and stays open into late afternoon; check seasonal hours); allow 3–4 hours to see major areas.
Quick hotel breakfast then head to Roma Termini to catch a regional or economy intercity train to Florence; regional trains are cheaper but slower—book seats early for the best value.
Admire Santa Maria del Fiore from the outside; if interested, consider a combined timed ticket for the dome/campanile/complex (ticketed and often requires reservation).
Choose a modest trattoria offering hearty Tuscan cuisine at friendly prices—arrive early for group seating or look for places off the main squares to save money.
Have a quick breakfast and take an early regional train to Pisa (about 1 hour); regional trains are cheap and frequent—buy tickets at the station or online for a small service fee.
See the Leaning Tower, cathedral and baptistery in a compact square; climbing the tower requires a timed ticket—reserve ahead if the group wants to go up.
Take an early intercity or faster regional train to Venice; booking in advance gives group discounts though travel time is ~2–3 hours depending on service.
Try several cicchetti at bacari for a varied and economical Venetian-style lunch—cheaper and more authentic than a formal sit-down meal in the busiest areas.
Wander the lanes, admire the skyline of medieval towers and visit small museums; walking the town is free and visiting Torre Grossa is optional with a fee when open.
Take the afternoon/evening bus back to Florence (via Poggibonsi if required); confirm return times so you don't miss the last service back to the city.