That is the filament of a light bulb at 4:1.
It's sort of a failed shot I tried to do. I didn't want to stop down much more than 5.6 (due to the loss in sharpness I would have gotten), and 1/4000th (fastest shutter speed on the 350D) wasn't fast enough to get the exposure I wanted.
I still liked the result (even though it wasn't what I was going for).
Imagine this exposed 3-4 stops less (maybe more...?) - that's what I was going for. I'll probably need some ND filters to get the shot I wanted.