FPS drop in certain areas (The Elder Scrolls 5: Skyrim)

I downloaded pure Skyrim on a fairly powerful hardware (much higher than recommended), I walk calmly at 60 fps on the map, but when I come to villages or cities, as well as near cities or near mountains, the fps sags a lot if you move the mouse a little, but if you take it a little then the fps will stabilize. what to do? there are no mods.