How does Facebook know where my pictures are taken?

[Cheeze]

I don't really frequent Facebook a lot, mostly to access fan pages and stuff. Anyway, a long time ago I uploaded some albums for my friends to see and I don't exactly remember tagging them or anything... They were uploaded at home, and at that time I had a crappy phone so definitely no location services or anything. Now at the left side of my Facebook (where ads are normally placed), Facebook asks if the photos in the album were taken at xx or yy place - and they were! I'd like to know how this is done, it's kind of... weird and stalker-ish .
Thanks in advance!

[Haulein]

It does the same with my iPod, whenever I take a picture, if there is any wifi at all anywhere, the location and ip address from it's router will save it's location, so when you add it to Facebook, the location goes with it