aerial view of hinterhaus castle ruins in spitz, wachau valley, austria

world waterway wachau views view valley unesco tree tower tourism terrain symbol surrounded stunning stronghold strategic stone stands spitz site served ruins rock river popular photographers perfectly perched overlook offering natural mountain monastery medieval lush landscape landmark history historic hinterhaus hillside hill hiking heritage green fortress fortification forests estate enthusiasts destination danube countryside century castle built building breathtaking blends austrias austrian austria castle austria valley ruins fortress aerial drone shot river ancient architecture european history destination site heritage scenic