This structure is located at the highest point of the McKenzie Pass Scenic Highway which travels through Willamette National Forest and the surrounding area. It is constructed entirely of volcanic lava rock and sits in the middle of a huge area (hundred of acres, probably) of the same, black rock. It was built in 1935 by the Civilian Conservation Corps.
The round building has an open area on top which affords the viewer an unobstructed 360 degree panorama of the area. The room below it has several large windows, as well as two “viewfinder” windows which point towards the mountains (see post below).