rhine valley, heritage region, medieval fortress, middle rhine, mighty castle, thein, upper middle rhine valley, blau, berge, himmel, sky, blue, fluss, wald, wood, history, deutschland, germany, flag, castle, burg, mittelalter, medieval, europa, rheinland-pfalz, historisch, buildings, unesco, fahne, rhein, historic, world heritage, festung, middle ages, haeuser, unesco world heritage, rheinfels castle, st. goar, rheinfels