Museum SAN is at 260 Oak Valley 2-gil; Sogeumsan Grand Valley starts at 317 Jijeong-ro in the Ganhyeon Tourist Area. They are separate destinations, not a walk between museum and trail. A two-stop day depends on the road or public-transport connection you can actually use.
Start with the earlier Grand Valley ticket window
The current visitor listing shows Grand Valley operating 09:00–18:00 from April through October and 09:00–17:00 from November through March. Ticketing is listed from 08:30 to 16:30 in the longer season and 08:30 to 15:30 in winter. It is closed on Mondays; when Monday is a public holiday, the listing says it closes the following business day. If both places are on the same day, this earlier ticket window makes Grand Valley the first stop only when the transfer still leaves time for the museum.
Keep Museum SAN as the optional second visit
Museum SAN operates 10:00–18:00 and closes its ticket office at 17:00; it is closed every Monday. Its visitor map estimates about 10 minutes from the Welcome Center to the Main Building, 15 minutes to the Meditation Hall, 20 minutes to James Turrell Hall and 5–10 minutes to GROUND. Those are walks inside the museum grounds, not transfer times from the valley. Check the route between the two addresses before deciding that both fit.
When one destination is the better day
Choose one anchor if a full museum visit or the longer Grand Valley course is the priority. If the return transfer is uncertain, do not rely on the second attraction as a short add-on: ticket cutoffs and travel between the sites are independent.
Check the latest Grand Valley facility notice, Wonju tariff page, and Museum SAN visitor information. For a ticket-by-ticket choice between the two, see the Museum SAN and Sogeumsan comparison.