The "Ape Caves" are lava tubes in Gifford-Pinchot National Forest, southwest of Mt. St. Helens.
156 miles, 3+h from Tacoma.
I-5 South 112 miles,
at Woodland, left - north-east on 503
Continue on Lewis Rd - east - to Cougar (don't take 503 south)
continue on NF 90 - east
Left (North) on 8303
3 miles
Nearby town is Cougar.
Also nearby:
Lava Canyon
http://www.fs.fed.us/gpnf/recreation/ape-cave/index.shtml
The lava tube is 13,042 foot (3976m) long.
Apes' Headquarters is located at Ape Cave on Forest Road 8303, 3 miles north of the junction of Forest Roads 83/90.
DO Bring with you
Three sources of light – Clean-burning lanterns (propane or white gas) or flashlights with strong batteries and bright bulbs.
Sturdy shoes/boots – The lava tube floor is uneven and covered with jagged rocks.
Warm clothing – The temperature remains near 42ºF/6ºC year round. It can also be windy and wet in the lava tube.
A friend – Also, let someone else know where you are going and for how long.
DO NOT:
No food, beverages, alcohol or littering – These items attract animals and bacteria that do not belong in the cave. Food and litter decompose at an extremely slow rate in the cool temperatures of cave ecosystems.
No smoking – Smoke lingers in the cave and is harmful to cave creatures and humans.
No flares, fireworks, firearms or any kind of open flame. These leave a residue and blacken cave walls.
No rock collecting or damaging cave features ($200 fine). Damage to features prevents you and future visitors from enjoying them.
No pets – Dog paws are easily cut on the jagged rocks. Animal feces damage cave ecosystems and is unpleasant to those who follow.
Do not touch the walls. A bacteria with fungus-like characteristics, called “cave slime,” lives on the cave walls. This slime is a food source for other cave life, is easily wiped off when touched, and takes many years to re-grow.
Two paths ... upper and lower.
The main entrance divides the cave into two sections, the upper cave and lower cave.
The three-quarter-mile (1200m) lower portion takes about one hour round-trip to complete.
The 1½-mile (2100m), upper portion of the cave takes about 2½ hours to complete, returning on a surface trail. Cavers must climb over approximately 27 boulder piles and scale an 8-foot (2.5m) high lava fall.