I stand corrected, apparently a company called KUERT Information Management claims to even recover data from overwritten parts of the discs, although this seems to apply to data the user thought was overwritten but is physically intact. I would like to see someone recover anything after overwriting a sector 10 times - there is no need to dip anything into acid.
Drives since the mid-90's are only low-level formatted at the factory due to the move to RLL and zoned/variable bit-rate recording and other technologies that allow us to cram ever increasing amounts of data inside one. The LLF utilities today just instruct the drive's controller to do a reinitialization, which wipes the contents of each sector back to a factory initialized state. What it doesn't do is rebuild the servo control data, sector preamble/postamble and error control blocks. If it's a fairly modern drive you should be okay, but, things could be a bit more expensive for you if you've done a high-level format from the operating system afterward. Worse if you started using the drive after that. Anyway, you're going to have to ship the drive out to a data recovery firm. Depending on work involved, it could end costing you a good chunk of change, hope the data is worth the cost and trouble. I'd start here based on personal experience, but there are other firms out there as well. http://www.ontrackdatarecovery.com/hard-drive-recovery/
U.S. DoD recommendations are 3/7 overwrites with random data. Gutmann recommends 35 times. The NSA doesn't stop there, you have to use an NSA-approved degausser as per: http://www.nsa.gov/ia/_files/government/MDG/EPL-Degausser30March2009.pdf YMMV...
Must be possible, as DOD requirements for classified information require incineration or shredding of the drive.
As you can tell from the varied responses you received, it would be most helpful if you told us if you are concerned with making sure that no information is recoverable from a drive you have formatted for privacy/security reasons or if you are trying to recover data from a drive that has been (accidentally) formatted. Two different subjects.
LL format should do the trick, but you can also use wave a large magnet over your drive, and this will eliminate any "disk residue" still left there.