So you have downloaded a lot to your game. Because you have placed it in your game it’s not on the original lot it was created on and now you have mountains or sinking. Do not fear. I was scooping out the forums over at the sims3 community and I happened to run across this problem. So what’s the solution you ask? Here it is. You must be in Edit Town and your sim cannot be on the purchased lot, move them to the clipboard (basically evict them). Get your cheat bar up, (shft+ctrl+c), type in setimportedterrainoffset(value).
What’s value? This is a positive or negative number. Positive raises the land, negative lowers the land. (so your cheat will look like this: setimportedterrainoffset10) Now, place your lot. WAIT…DON’T HIT THAT “OK” BUTTON YET! Check your lot, is it where you want it? No? Hit cancel and do the cheat again. Keep repeating till you get your lot the way you want it. You can also use decimals to fine tune your lot. This information was provided by simmer, Crinrict.