This cover from Portugal depicts a single stamp issued in 2023 celebrating the 17th. century
fortresses of the border city of Elvas, classified by UNESCO as World Heritage site for its uniqueness in the world.
The site, extensively fortified from the 17th to 19th centuries, represents the largest bulwarked dry ditch system in the world. Within its walls, the town contains barracks and other militar buildings as well as churches and monasteries. While Elvas contains remains dating back to the 10th century A.D., its fortification began when Portugal regained Independence in 1640. The fortifications designed by dutch jesuits represent the best surviving example of the dutch school of fortifications anywhere
