This is the Frecha da Mizarela, which is usually referred as the highest waterfall in Portugal, at least in the continent, as I have a vague idea that in the Azores islands there is a waterfall slightly higher. It's 75 meters high and it's located in the scenic Serra da Freita, in the municipality of Arouca. About 1/4 or 1/3 of the total height isn't visible here, because the lower part is hidden by the slope of the foreground.
According to the Portuguese dictionary I consulted just now, "frecha" means arrow, but I always thought it meant the same of "fresta" (crevice, crack). Mizarela is the name of the tiny settlement located to the upper left of the photo.
I found only other two post of this waterfall in TE [1, 2].
As you may guess, the day was quite cloudy and that wasn't the only thing against great photos that day, as I was returning home in the end of a weekend with my wife and son using the longest route, which often makes them impatient, specially if it is 7pm and we are at least 3 hours away from home. Somehow I wasn't so unlucky as the rain stopped for a while when I reached the site of the waterfall and came again before we reached the main road.
WS: Alternative view.
Location (latitude, longitude): 40.8627,-8.2831