Leave after 08:00, be back for dinner. These are doable without a tour bus if you can read a Korail timetable.
Walkable UNESCO fortress. Combine with a beef-rib lunch. Skip if you already did four Seoul palaces and are fortress-tired.
Passport required for most tours beyond Imjingak. Book official tours; do not freelance to the border.
Pretty in snow and autumn. Weekends are packed. Gapyeong also has Garden of Morning Calm if Nami is sold out.
Half-day food + waterfront. Easy if your flight is the next morning from ICN.
Sea + coffee street. Tight as a day trip β better as an overnight unless you take the first KTX both ways.
K-drama scenery. Best in spring/autumn; summer is humid on the hills.
Book the fast train on the KTX page. Full itineraries: ready-made plans.