The cave was discovered in August, 1931, when vapor was observed issuing from small crevices in some rocks. In the spring of 1932 it was opened commercially. After six months the commercial venture was abandoned as revenues did not justify operation. The electrical equipment was in good condition when the cave was visited in 1947. The property was bought in the early 1960’s by J. Bernard Wilt, Rockville, Maryland. Due to increasing vandalism of the cave, Mr. Wilt sealed the entrance soon after acquiring it; and the cave remains closed.
     Several MGS staff geologists visited Mt Aetna Cave in February 2005 and found the electrical system rusted away. 

Medium- to thick-bedded, medium-to coarse-grained, intraclastic grainstone, tan, laminated dolostone and dolomitic limestone, and medium-gray, oolitic, lime grainstone, ribbony carbonates and burrow mottled dolomitic limestone. This unit is typically poorly exposed, but makes up the greatest thickness of the formation. Is is best exposed at the quarry at Cavetown. Thickness estimated at 200 to 300 m (600 top 900 feet).

     The entrance to the cave is in a small wooden building 30 feet above and 50 feet east of the road.  A flight of concrete stairs descends 15 feet to the floor of the cave.  The main passage of the cave is a straight level tunnel varying from 10 to 15 feet wide and 8 feet high.  At places formations are so dense that the passage is restricted to 2 or 3 feet in width.  A short flight of steps 37 feet from the entrance leads to a roomy passage on the east. A large column necessitates a detour in the main passage just south of these steps.  For the remaining 354 feet of the main passage the cave is beautifully decorated by myriads of stalactites and columns. Delicate “soda straw” stalactites abound mixed with an abundance of “carrot” types.   Bacon rind with unique fluted edges as well as some flowstone add to the decorations.  These formations were so dense at the time of discovery that a passageway had to be cut through them.  The passage terminates in a low tunnel 4 feet wide and 3 feet high that pinches out 30 feet beyond the end of the large passage.
     The upper passage leaves the main passage at a point 37 feet from the entrance where narrow stairs on the east lead upwards for 10 feet.   The upper level consists of three rooms connected by low narrow passages.   The northern room, measuring 40 feet long by 18 feet wide, with a ceiling 15 feet high, is the only one developed for public inspection.  It is filled with numerous formations similar to the main passage.  On the north side is an opening through which the original entrance to the cave was made.  A set of clay-covered parallel passages, each 2 feet in diameter, lead off the northeast end of the room and can be traversed for 30 feet.
      At the southwest end of the room a formation- choked passage, 4 feet in diameter, leads 25 feet to an undeveloped room 40 feet long by 12 feet wide.   The slope of the floor is irregular due to fallen rock.   The ceiling is made of thousands of delicate “soda straw” and “carrot” stalactites that show two distinct stages of interrupted growth. Columns and large stalagmites clutter the floor and in places are so dense as to block passage.
     The third room is offset and connected to the southwest end of the middle room. This room has a ceiling height of 4 feet and is 20 feet long by 15 feet wide. Formations are less plentiful and are found along the west wall where a series of short columns line a low shelf. A passage 15 feet long and 2 feet in diameter leading off the southwest end of the room is choked with formations.

(from ES3 -Caves of Maryland)