1. I was taking a night walk with my husband in Monsanto village, in Portugal.2. The village is located in an elevation and from there we have panoramic view for all the surrounding places, and I was facing East from a descending street in the same direction.3. 'There goes an UFO'.4. It was around 22.40pm. The sky was full of stars because there are few city and village lights interfering with the sky viewing, no clouds that night, summer breeze and 24C/75F of temperature. It was green light, round shaped, it looked like a green traffic light because of it's color and brightness. It was going in a fast speed from West to East, Spain direction. The object only took 2 seconds covering a distance that a plane covers in about 20 seconds. It was probably more than 1 mile high, and at least 2 miles away from the place I was.5. Since it wasn't the first time I saw an UFO, I knew what I was seeing in that very same moment. I sometimes 'know' that something is going to happen a few minutes or hours before it happens, and sometimes 'something' makes me look up, like someone is tapping me in the shoulder and saying to me: 'look up, now'.After the sighting I went to a terrace in the place I was staying, that has a panoramic view from the village surroundings and an incredidle sky visibility, stayed there for 40mn searching the sky but had no luck. The night after I spent 3h looking the sky between 9pm and 0am, but had no luck in a new sighting.6. I was gone in a blink, like it was vanished in the air.