"Out on the South Salem Road (present Highway 16) there was a brewery built in the coulee opposite the Keppel farm. Some time in the late 1850's a man name Diefenthaler operated it."
The article says little more, indicating that the dates were unclear. It did mention that there was a pavillion, a dance hall and an excavated storage cave.
That was plenty to get me looking. Highway 16 of course still exists. On line plat maps from the era of the newspaper article showed a property in the name of Keppel. Switching over to Google Earth I could see a valley on the far side of the highway, with a nice bluff and a little stream. It had to be the place.
And it was.
From the outside looking in:
It is not a very big cave. As you can see it has some old furniture in it. Unwisely these occasional inhabitants have been lighting fires inside. This is a bad idea from several perspectives. Not only is there danger of weakening the roof, the ventilation in caves is somewhat suspect and carbon monoxide poisonings have been known to tragically occur.
A peculiar feature of this cave is that there are no vent holes in the roof. But there are what appear to be four vent holes in the sides of the cave. Notice that leaves have fallen down from above.
Once this cave was protected by heavy iron gates, the hinges of which are still in place. Now it is open, and with the caution mentioned above, there does not appear to be any problem visiting it. If you are feeling a bit lazy and don't think I have supplied enough clues I can add that it is in a nature preserve and near an abandoned tavern, one that I suspect is on the site of Mr. Diefenthaler's long ago dance hall and pavillion.