Ooo CSquared, in other words, I could *cough*expand*cough* my property by making a garden or personal fishing spot without actually using my lot! Hmmmm this has possibilities!
With limitations, as Chronic mentioned. I've always longed to create a butterfly garden by using insects spawners next door to an active household. No sense in cluttering it up with townies! Or, yes, a fishing spot,
THE fishing spot. Or, if you wanted, you could have your Sims purchase the lot and use that as a museum lot for your legacy or whatnot, to hold graves and/or portraits or whatever.