Gastein (gäˈstĪn) [key], valley, Salzburg prov., central Austria, in the N Hohe Tauern range. A popular and beautiful resort area, it has hot radioactive springs. Badgastein, one of the most fashionable spas in Europe, and Bad Hofgastein, also a resort, are found there. Gold and silver have been mined in the region since Roman times. Near Badgastein, the Gasteiner Ache River (c.25 mi/40 km long) forms two waterfalls. There is a hydroelectric plant near the mouth of the river, at Lend.