I was riding along Pacific Highway towards Downtown and was crossing the San Diego River at Mission Valley when I saw some smoke. I followed a trail as far as I could and then I had to park my bike and climb a fence and cross the trolley tracks. About a quarter mile past there, just below Interstate 8, there was a small brush fire burning. Firemen arrived shortly after I did (from the opposite direction). It was small and was pretty much burning itself out at this point- the only damage was some burned grass and a palm tree, but it was interesting for a few minutes. Again, why it is a good idea to carry my camera at all times.