It's also on the Snake River in Murtaugh. I'm trying to find the road you take and then you have to watch for a sign and drive down a dirt road. It's kind of hard to find. The last time I was there, you could park in a small area at the end of a farmer's field or if you had 4WD or a car with a bit of road clearance, you could drive down a fairly steep dirt road to the bottom. I'll post when I find a map or better directions.
Cauldron Linn, also known as Caldron Linn or Star Falls, is on 1475 S as near as I can tell. If you google it, you'll find lots of pictures and some directions. It's worth seeing! And have you been to Hells Canyon?