The Garrison Border Town of Elvas and its Fortifications was inscribed on the UNESCO World Heritage list in 2012 as the largest bulwark fortification system in the world. The 17th-century walls — twelve bastions arranged in a star, a dry moat, and a complex series of outworks — were designed by the Dutch military engineer João Pascácio Cosmander on the most advanced principles of his day, and they encircle the entire old town.
You can walk the full circuit of the inner walls in about ninety minutes. From the ramparts there are uninterrupted views east to Spain, and the surrounding satellite forts — Fort Santa Luzia and the Forte da Graça — sit on the horizon. The walls are free to enter and largely unrestored, which is part of their power: you can climb them anywhere, and the only company is usually the wind.