a geodesic mark crowns the top of monsanto's ancient castle in portugal

landmark tower monument rock ruins terrain sea coast cliff fortification tourism temple vacation geology building mountain horizon geodesic mark crowns top monsanto 39aph39 ancient castle portugal historic site offers stunning panoramic views surrounding countryside blending history nature serene setting hilltop stone landscape viewpoint fortress architecture medieval sky outdoors travel rural hiking scenic heritage mountaintop european blue exploration formation cobblestone path summer adventure tranquility high altitude