I found it!

3,875 feet (1,181 m)

45°08′00″N 122°17′22″W / 45.133333°N 122.28944°W / 45.133333; -122.28944 (Clear Lake (Clackamas County, Oregon))

This isn't easy to get to, if you don't know where you are going. The road NF45, then a branch of NF4510, requires high-clearance vehicles. Lots of big holes and rocks, but a beautiful area.

 Sorry, forgot the camera (as usual) - these were taken with my iPhone.

The TW200 taking in the lake view after making the journey easy. What you can't see in any of these images, is that this lake is surrounded on three sides by mountains (very close).

These flowering bushes were everywhere...

Another lake view.

The lake is much longer than wide. Such a great, isolated place.