So i tried testing some terrain stuff, and wanted to use heightmaps to recreate some real world locations. I downloaded one from Cities: Skylines map generator (skydark.pl), but when i imported the raw file to the terrain object, it created a spiky mess, that resembled the terrain only from afar. I tried searching on the internet for solutions, but none of them fixed my problem. Unity version is 2020.3.39f
Looks like you just have the vertical scale jacked up way too high.
Try 1/10th as high (the Terrain Height setting within the settings for the Terrain object).
Thank you, i forgot how flat the Earth is.