It is possible that you didn't actually format the disk (quick format of some kind). Its also vaguely possible that if you did a forensic disk specialist might recover something useful.
If it is a truly low-level format with disk manufacturer supplied software, which will zero fill your disk plate, then you can't retrieve anything back, except disk geometry, physical setup information come with every hard drive.
If ure that much paranoid about the contents stored on the HD, I suggest you drill a couple holes through the damn thing and let it soak in a jar of Coca-Cola (although I prefer a raw bleach) overnight.
I've been told by computer guy who does LOTS of systems, "nothing recoverable after LLF". May not be 100% accurate, but you may need forensic software, if possible at all.
The answer is only as good as the question and the question lacks specifics. What's going on and how important, if at all, is recovery?
Nothing is recoverable in that case, basically once you write over the sectors (or do the so-called LLF) there is no way to recover anything since it's magnetically impossible.
Unless the plates are pulverized and dipped in high grade amino acid, up to 90% of the vileness on your drive can be recovered and used against you in 43 states.
Unless the discs inside are literally destroyed, i.e. melted with a blow torch or something, there is ALWAYS a way to retrieve data off a hard drive. Even then, I would bet the NSA or some government agency would still be able to recover data. Even if the drive has "failed" and is not usable anymore, you can take the platters out and read the data in another device. There is software that allows you to recover data after formatting your hdd. If you used a program like DBAN or Acronis to wipe it, you'll probably have to take it to a data recovery center. Hell, even a place like Best Buy Geek Squad can do this. They'll recover all your data for a cool 2 grand if you format the drive or it has failed. I wish people would just not post about topics they have no knowledge about.