Its diameter is1436 km, and it was found in 1671 by Cassini.
It orbits an area within the radius 50 times that of Saturn's.
The weirdest thing about this moon is that, when it's on the east side of Saturn, its gets as much as7 times brighter! It's thought that one side of the moon has a light color and the other has a dark color.
Well, this looks like something is going on, I hope there was a probe to Iapetus to go find out why it's so weird.
For the moment, it's said that the dark stuff is residue from evaporation of water ice from the surface.
There were a few cool pictures of Iapetus on the web, so I'll post a few. Enjoy!