Today, the border between Spain and Portugal is hardly visible, but in centuries past, it was heavily fortified and fought over. There is a fair number of fortified border towns in both countries (some of them also striving for WH status), but the best one is certainly Elvas, guarding the approaches to Lisbon on the main road from Madrid and Badajoz. Fought over various times throughout the centuries (with the Spanish and Portuguese sometimes on the same side, as in the Napoleonic Wars), Elvas is a great example of military architecture. The town is surrounded by massive walls and has several huge forts outside. I spent quite some time in the biggest one, Santa Luzia, which also features a military museum. This fort and the castle of Elvas, dating from Arab times, both offer great views over the surrounding area and give an impression of the strategic location and importance of the town, which also features several interesting non-military attractions, especially the Amoreira Aqueduct and the beautifully decorated Dominican Church. Elvas is definitely worth a day of exploration, and is conveniently located between Mérida and Évora.