Built on a high hilltop of jagged quartz, Marvão's has an excellent position and vantage point in a mostly flat landscape. Along the border to the north, the mountains are higher, and snowy ranges like the Serra da Estrela provide a natural break between the two countries. In this lower land, outcroppings like this define the boundary. To this day, in land further south, there are disputes about the actual division, where old contests have never fully been resolved.
The castle has an unusually long outer wall, which is essentially intended to cover as much of the hill's flat top as possible. It extends from the main keep to a secondary gate complex, which accesses the town of Marvão, which is itself walled. The keep sits atop the steepest point, with solid rock underneath and a secondary tower alongside. In the rear, terraced battlements step down underneath, constructed as more room was required for cannons.
While the outer walls are low and, frankly, too long to be effective (the castle was taken several times, it's not the epitome of defensibility), both the central stronghold and the gate complex are very well protected. One feature of the entrance: behind the door, there is a curving corridor, almost overhung by small towers and firing positions, making it difficult to proceed inward after the entrance was breached. The Marvão's main weakness is that the two defensive focal points are separated by such a long length of wall, without towers and requiring a large force to defend.
Another weakness - as it is with many castles - is the lack of water. The hard quartz under the walls was a great foundation and discouraged tunneling, but also made digging a well impossible. This is a very dry climate, with a deep water table. So, a large, covered cistern was built to collect rain water in case of siege. This is perhaps the most echo-ey place I've ever been. Our camera shutters rang out like slamming doors.
Although it's importance increased when Portugal and Spain began to congeal into nations, Marvão has been defended since Roman times, and was the site of an important battle between the Ceasar's troops and an army from Pompei. It's defenses were expanded by the Moors, and then by the Christian "reconquista" forces. The genesis of the present form was really only begun in 1300, though, when Portugal's nascent nation was beginning to seek out its inland boundary. The inner buildings retain a lot of Moorish character, and the courtyards feel especially Portuguese, with tiling and whitewashed walls.
It was some three centuries later, after the entire Iberian peninsula had been semi-united under the Spanish Hapsburgs, that the castle saw the most action. The Portuguese Restoration War, as it is known, was a revolt and separation from the Spanish, and was fought in large part along this border. Although it largely consisted of skirmishes and raids, it lasted for 28 years and Marvão was among the leading strongholds. Even after a peace was attained, the region was uneasy, with the neighboring sides maintaining an armed presence for two centuries, and re-engaging in the Peninsular War (part of the larger Napoleonic wars) between 1807 and 1814.
Today, the castle seems cut off from the rest of Portugal, being too far inland for the coastal tourists. There is no admission, no attendant, no signage or information - remarkable for such a large and impressively preserved castle. Walking around, we saw only two other tourists and a man who was fixing a streetlight. There'e little chance of war with Spain these days, and both countries seem to be facing away from this line.
The view from the top of the keep is spectacular, a countryside of cork and olive trees stretching out into both realms, almost empty of houses and people.