San Marino is tiny -- the entire country is just 61 square kilometers -- so getting around is straightforward.
The historic center of San Marino city is pedestrian-only and easily explored on foot. Be prepared for steep climbs, particularly on the path between the Three Towers along the Monte Titano ridge. Wear comfortable shoes.
A local bus service connects San Marino's nine municipalities, including Borgo Maggiore, Serravalle, and Domagnano. The cable car (funivia) between Borgo Maggiore and the historic center runs regularly and is the most enjoyable way to travel between the lower town and the summit.
If you have a car, you can drive between the towns easily, though parking in San Marino city itself is limited to areas outside the old walls. The country has well-maintained roads and no tolls.
Most visitors see San Marino in half a day to a full day. The walk along the ridgeline between the Three Towers takes about an hour and is the highlight of any visit.