A few minutes googling the internet provided the answer--stalactites, stalagmites, and the columns they form are sometimes considered to be naturally occuring lingams, representations of Shiva's power and the male principle (in some formations, the male + female principle). It seemed that the monks and visitors from the subcontinent were looking at an American variant of the Amaranth temple dedicated to Lord Shiva, located in Jammu and Kashmir, India.
Instead of garlands and milk, the only religious symbolism in Luray was the "Stalacpipe Organ" (really sort of a xylophone) that played "A Mighty Fortress Is Our God" with its hammers tinkling the hanging stalactites. (You can listen to "Red River Valley" here. Or another tune here...)
The whole experience was somewhat supernatural--Luray Caverns are well worth a visit, for both the natural wonders and the human beings who experience them. There's also a car museum, which has a nice collection of sleighs, carriages, and vintage Hudsons, DeSotos, Model Ts, Stanley Steamers, as well as Rolls-Royces that belonged to Pola Negri and Rudolf Valentino--of all things, in all places...
360 degree views, here. And here.