The Romsdalseggen is regularly named among Norway's finest day hikes. The route runs along a narrow ridge above the Romsdalen valley, with the Trolltindene peaks to one side and the fjord to the other. It is about 10 km, takes seven to nine hours, and involves real exposure in places — there is a short chain-assisted section and a fair amount of scrambling. It is not a route for vertigo sufferers or for bad weather.
Most walkers take the early-morning shuttle bus from Åndalsnes up to the trailhead at Vengedalen, then walk back to town. That way you do the hard climbing first, the ridge in the middle, and you descend straight back to the railway station. Bring proper boots, plenty of water, a wind layer, and a paper map: cloud can move in fast and the ridge is no place to be lost.