Grab coffee and a fresh croissant or sandwich at the station bakery so you travel light; most station bakeries open from about 6:00am. Good fuel for the short train ride and the hill walks in Sion.
Take an InterRegio or regional SBB train east from Martigny to Sion; journey time ~20–30 minutes and trains run roughly every 30 minutes. Buy a point-to-point ticket at the machine or via the SBB app.
Visit the hilltop Basilique de Valère for panoramic views over Sion and the Rhône valley; the funicular and site are generally open from about 9:00am in high season — verify exact hours on arrival.
A short walk from Valère, the dramatic Tourbillon castle ruins sit on a neighboring hill and are free to explore outdoors — great photos and historical context for Sion's medieval past.
Descend into the compact old town to wander cobbled streets, see the cathedral squares and local shops; this is a relaxing way to absorb the town's atmosphere before lunch.
Eat Valais specialties (raclette, dried beef, rösti) at a nearby bistro in the Old Town; many bistros serve lunch from about 12:00–14:30. Ask the host for regional wine suggestions.
Learn about local history, archaeology and culture; the museum typically opens around 10:00 and closes around 17:00 (check current hours), making mid-afternoon a good visit slot.
Walk along the Rhône and up to a nearby vineyard viewpoint to enjoy the valley views and see the local grape terraces — a peaceful way to experience Valais scenery without leaving Sion.
Take a coffee break or enjoy an apéritif in town; many cafés remain open until early evening (around 17:00–18:30). This is a good time to relax and plan evening travel.
Dine on regional dishes at a sit-down restaurant in Sion Old Town; most restaurants open for dinner from ~18:00 and offer local wines and hearty Valais cuisine.
Return to Sion station for a westbound train back to Martigny (trains run late into the evening). If you prefer, you can stay overnight in Sion; consult the SBB app for the exact departure times and platform.