Leaving Spain...and entering Portugal.
Time to head west and into new territory - Portugal.
The dry countryside to the border is fairly sparsely populated with few villages or towns and with much larger farms than we had seen to date. The roads had few cars and even on the smaller roads it was easy driving.
In the distance not far from a tiny village called Sanlúcar la Mayor we saw two huge towers that seemed to have an incredibly bright light emanating from their tops. We couldn't work out why such a light would be on in broad daylight but then we recalled a newspaper article we had recently read about a new kind of solar power plant involving the fusing of salt to provide a 24 hour energy source but still in the experimental stages. We thought this might be it so we tried a few side roads to get closer and eventually found the right one which led us right up to the towers. The towers themselves were not emitting light but receiving it from a vast array of mirrors all angled towards the top of the tower. Against the clear blue sky, a distinct ray of light came from each mirror with all of them concentrated at a receiver on the tower. Two more towers were under construction and all around were different arrays of mirrors, of different shapes - curved, parabolic, flat - and arranged in different ways - in rows, in a circular arrangement on pillars, in tiers. All obviously cutting-edge, experimental stuff. After driving away, we looked back for another view and were stunned to see that on one of the towers, the focal point had been moved away from the top of the tower and there was a new pattern of the light rays intersecting then streaming out into space. We surmised that this could have been to allow the tower to cool so further worked could be done, but we were only guessing.
And on we went crossing the border over a long bridge over the Rio Guardiana which forms the natural border between Spain and Portugal. No border formalities now within the EU so we entered the southernmost province of Portugal, the Algarve without stopping.