Son and I saw a dark spherical object hovering in the sky over the valley

We were walking back down the trail from the observation tower toward the area where there's a bust of Beethoven on the north northwest side of the path. My son (14) had sat down on a bench and said, "Hey Mom, there's a UFO!" I sat down beside him and we watched what appeared to be a small, dark spherical (maybe metallic?) object hovering over the valley below in a north west direction. It seemed to be pretty far away and high up, as it was small. It stayed almost in one place, but seemed to be getting smaller/further away (it seemed to be going away from us). We watched it for a couple minutes until it was obscured by the clouds. The clouds were moving in a south west direction, if I recall correctly. It did not appear to be drifting in the wind, but under its own power.
I am a 51 year-old female, well educated, with a masters degree in the experimental analysis of behavior.
The attached photos were taken just after we saw the object, as we were continuing back down the path to the palace.
It did not occur to me to take a photo of the object, plus it was so far away I don't think the camera would've picked it up. I marked the approximate location on Google maps and copied it to the location box.