There is a lot to see and do in Quinault Rain Forest, starting with the trees. Go to "Valley of the Giants" to find out about all the record size tree in the Quinault Valley.
Waterfall are also a feature you will see in Quinault Rain Forest, an excellent website Waterfalls of the Pacific Northwest.
Numerous trails through the Rainforest are located around the lake and up the Quinault Valley. Many guidebooks do not list all of the Trail you can walk because some are found on the South Shore of the Lake, which are US Forest Service trails and some are on the North Shore, which are through Olympic National Park. The many differing trails each has it own secrets to share. A temperate rainforest can't be seen accurately at a mere glance. Hillside have different make ups than valley floors, north sides of hills are not the same as south. The Trail Map will help you explore this.
Here is a link to back country trails leading from Quinault.