Start with the compact historic centre
1. Walk the cathedral-to-Serdica route. Begin at Alexander Nevsky Cathedral, then pass St Sofia Church, the Russian Church and the National Theatre before heading to the Largo and the exposed Serdica ruins. It is a manageable 2–3 km route with plenty of stops, so allow half a day if you enter churches or museums. Dress modestly for active Orthodox churches and keep in mind that services can limit sightseeing access. The ruins are beside Serdika metro, which makes this an easy first stop from the airport line.
Choose one museum or indoor stop
2. Use the National Archaeological Museum for a concise historical overview, or the National Gallery complex for art. The Rotunda of St George is close to the Largo and takes little time, but it is not a substitute for a museum if Roman and Thracian history is your main interest. Check current opening days and ticket rules before planning a Monday museum day. Vitosha Boulevard is best used as the walking link between the centre and NDK, not as an attraction that needs several hours.
Make Boyana and Vitosha separate decisions
3. Visit Boyana Church if the 13th-century frescoes are a priority. It is on Sofia’s southern edge, has controlled visitor access, and is easiest by taxi or bus plus a short walk; check the official opening timetable and whether photography is restricted. 4. Go to Vitosha Mountain only when weather and trail conditions support it. It is a real mountain outing, not a city park. Verify the current bus route, lift operation and marked trail conditions, particularly outside summer. Give either Boyana or Vitosha at least half a day rather than cramming both around cathedral visits.
Use the metro, then walk
Sofia’s centre is easier on foot than it first appears, while the metro is the sensible link for the airport and longer cross-town trips. Buy the current ticket type from the official transport system rather than assuming older paper-ticket advice still applies. With one day, do the cathedral, Serdica and one museum. With two, add Boyana or Vitosha. Plan meals near your route through where to eat in Sofia, and select a base based on your arrival and late-night plans in where to stay.