25 July 2012
American cave with underground river has carvings similar to Koonalda cave, Australia, lattice or grid pattern
Koonalda cave, Australia, carved lattice pattern
Seneca cavern, Ohio, carved lattice or grid pattern
If one compares this grid to a profile of the cavern system (last photo), it seems the grid could be a kind of map. There are seven levels to the cavern and seven "ladder sections" in the middle of the grid as seen below.
There were other possible art features in this cave which I plan to return to with better lighting and photography equipment. It seems North American cave art needs to be more thoroughly investigated. The landowner said no one had ever examined Seneca cavern for art before my visit.
A second 15 cm grid was next to the larger grid. (click photos to expand)
A profile map of the Seneca caverns, Bellevue, Ohio