Today we visit the Ancient Appian Way, catacombs, and Piazza Navona with optional shopping. Optional: A visit to Vatican City (technically not in Rome as it is a separate country) to see Saint Peter's Square and Basilica and Vatican Museums could be taken instead of going to Via Appia Antica. Be sure to book your Vatican Museum tickets or tour in advance.
Via Appia Antica and Catacombs
The Via Appia Antica, the major road of the ancient Roman Empire, is now a regional park, Parco Regionale Dell'Appia Antica. Take bus 118 or 218 to visit the catacombs of San Callisto, the largest and most impressive of the catacombs. Then walk or rent a bike and ride along the ancient road, lined with tombs, monuments, and churches. A beautiful place for lunch is the Cecilia Metella Restaurant, especially when it is nice and you can sit on the patio.
Tip: You can buy bus tickets at a newsstand or tabacchi. Validate them in the little machine when you board the bus. If you say catacombs, someone will tell you when to get off.
Spanish Steps and Shopping
If you have time in the afternoon, go to Piazza del Popolo and walk along Via del Corso, the main shopping street. Turn onto Via Condotti and follow it to the Spanish Steps. Window-shopping and people-watching is good in this area and won't hurt your budget. Read more about Shopping in Rome
It's fun to try a restaurant you've discovered on your own and after three days of walking around Rome, you've probably found something you'd like to try.
Piazza Navona and Tartufo
In the evening, Piazza Navona is a great place to continue your people-watching as well as see the three lavish Baroque fountains. The much-touted ice-cream dessert, tartufo, is said to have originated here - you can try it outside at the Tre Scalini for a splurge.