If I buy hilly abandoned land can it be terraformed and the hills brought down?

[sagia]

If I buy abandoned land and it is very hilly can the hills be dropped down with terraforming?

[Lindal Kidd]

Within limits, yes.

On the Mainland, terraforming is limited to +/- 4m, measured from the elevation at which the land was originally created by Linden Lab.  If a previous owner has already moved it up (or down) the maximum amount, you cannot move it further.

On private estates, the terraforming limits are +/- 100m, but this is often restricted by the estate owner to a lesser amount, or none.  Read the covenant carefully to see what terraforming is allowed, and if you are unsure, ASK before paying money.