Is It Talus Or Scree
Don't be fooled by the listed distance. This is a short but fairly difficult hike requiring caution to avoid injury. A hiking stick would certainly help.
The hike starts from an informal trailhead( unmarked) at 2.7 miles south of Spearfish, SD. The shoulder of the road is paved here for about 100 yards on the west side of the road. Cross over to the east side of the road and walk along the shoulder for about 100 feet. There is a trail going down the embankment here. It becomes difficult to follow in the summer as the vegetation can hide it. You are following along a creek. The trail eventually goes down again towards the creek. Continue north on the left side of the creek for about 75 yards. There are two crossings here as of this writing. The first involving tree branches, the second an amateur but pretty decent built bridge. Take the bridge across the creek and veer right. In about 50 feet you come to a boulder field, veer left and you should be able to see the trail visible past the 100 foot boulder field. This trail passes thru thick forest for about 100 yards and it comes to a chute going up.
There is not much of a trail from here on especially if there is water flowing down this Talus/Scree chute. It gets steeper and steeper as you negotiate the rocks finally arriving at the cavern. Take your time enjoying this seldom visited site and when you are ready you can take a well worn trail further off to the right of the cavern for some great views of Spearfish Canyon from the rim. When you've had enough return the way you came.
WARNING! Hiking and outdoor related sports can be dangerous. Be responsible and prepare for the trip. Study the area you are entering and plan accordingly. Dress for the current and unexpected weather changes. Take plenty of water. Never go alone. Make an itinerary with your plan(s), route(s), destination(s) and expected return time. Give your itinerary to trusted family and/or friends.