Three days is enough for a first look at Rio if you set priorities. This plan is an editorial way of organizing the trip, not a tour package: change the order to suit your accommodation, the weather, and available bookings. Before adding a stop, think about how much time you want to spend there and how you'd continue to the next one.
Day 1: a day along the coast
Pick a stretch of Copacabana or Ipanema as your starting point. You can walk, take a break, and spend time on the beach without trying to cover the whole coastline. Arpoador is another option to round out the outing; add it only if getting there and the day's conditions fit your plans.
For lunch, look for an option close to where you are. Going back to your accommodation in the middle of the day can be practical, but it's best to plan for it from the start. A simple first day also helps if you've arrived on a long flight.
Day 2: choose your big view
The idea is to make the Parque Bondinho Pão de Açúcar your main activity; its route connects Praia Vermelha, Morro da Urca, and Pão de Açúcar. Check tickets and conditions on the official website before setting the rest of the day.
Leave some margin around your booking so you can arrive and leave without rushing. Avoid committing to another timed visit immediately afterward. If the weather forces a change, check the conditions of your ticket and use the culture day as an alternative.
Day 3: a cultural visit and room to explore
Choose between the CCBB program and a visit to the Museu do Amanhã. If you want to do both, make sure the dates and times work together and check how you'll get between them. You don't need to fit in two museums to make the most of the day: one exhibition that interests you and a quiet break may be enough.
How to adjust this itinerary
If you're traveling with kids, older people, or someone who needs frequent breaks, shorten the distances. If you already know the coast, you can spend more time on a themed visit to the Jardim Botânico. And if a booking isn't available, rearrange the days before replacing it with an activity you're not interested in.
Sources for planning your visits: Riotur guide ↗, Bondinho ↗, CCBB ↗, Museu do Amanhã ↗. Confirm operating details for your dates.