First solve the trip to Danyang
Danyang County currently lists direct intercity-bus access from East Seoul and rail access from Cheongnyangni, with other approaches connecting through regional hubs. That makes the town itself relatively easy to reach without a car.
The harder part is the final local leg
Do not assume that an attraction shown close on a map has frequent public transport. Danyang's own visitor information for some outer sites shows only a small number of local-bus departures per day. Treat the trip from Danyang Station or the bus terminal to the attraction as a separate planning step.
Build a no-car day around clusters
A practical approach is to group sights in the same corridor, use local buses for predictable legs, and keep taxis as a backup for the last segment. If you are visiting a cave, museum, mountain entrance or riverside site outside the center, check that site's current access page rather than relying only on a general route-planning app.
Before you leave
Confirm the exact arrival point on your rail or bus ticket, then check the final local departure and the return trip. Rural frequencies can change by weekday, season and service adjustment. If the return bus is critical, leave enough time to switch to a taxi rather than planning a tight onward train connection.