The Lines of Torres Interpretation Centre is the sensible first stop in Sobral. It explains the network of forts, roads, signalling points, and scorched-earth planning that protected Lisbon during the third French invasion of Portugal.
The centre is small, but it gives the outdoor sites context before you climb to Alqueidão. Without that background, the earthworks can look like anonymous mounds. With it, the surrounding hills start to read as a deliberately engineered landscape.