Gray sphere hovering over our backyard at an altitude of 3000 feet.

I was 13 and living in Lima, Peru at the time playing in our backyard with my 2 brothers when we saw a large gray sphere hovering over our backyard. We quickly went upstairs to the roof to observe it better. The object was perfectly spherical and solid, it was gray in color like made of some kind of metal but had no trace of rivets, bolts, or joints. The object stood stationary above at an altitude of about 2000 to 3000 feet. It wasn't drifting with the wind nor exhibiting any vertical or horizontal movement, it was perfectly still. Initially I thought it may have been a balloon but it did not behave like a balloon nor did it have the telltale signs that balloons have, it seemed solid and was perfectly smooth and spherical, it had no movement whatsoever and did not move with the wind. The object had no windows, no engines, no lights. It was almost like "parked" above us.
After about 30 minutes, the object started ascending in a perfectly vertical direction at a very high speed until it was impossible to see. From the time it started moving until we couldn't see it any longer. I estimate that from the time it started ascending until we lost sight of the object it must have been less than 20 seconds.