I visited the park in April, 2005 and took these spring pictures. The park includes over 50 miles of trails, camping, and good views of the Spokane River. Most of these things are best enjoyed in Spring, when the weather is pleasant, the flowers are blooming, and the ground is moist.
The main attraction is the Bowl and Pitcher, which are maybe these guys:
These are basalt rocks, the taller over 50 feet high, along the Spokane River.
From the viewpoint, you're about 100 feet above the river, enough to make the big rocks look like pebbles, and induce a bit of vertigo.
Some rafters went by, which might help to establish a sense of proportion.
There are other rock formations in the area.
There's also a nice walking bridge, modelled after the original CCC one.
The Civil Conservation Corps did a lot of nice things for Spokane area parks, as well as across America.
Here's part of the picnic/camping area along the river.
If you go, have fun!