Soyanggang Skywalk is a transparent-floored walkway pushing out over the water near the centre of Chuncheon. It is short, a little theatrical, and very popular for photos, but the view does its job: water below, ridges beyond, and the city close behind you.
Go late in the day if the weather is good. The glass is the gimmick; the light over the river is the better reason to be there.