Is it one of them jacking points for big jacks like they use for off road things to make it easier in the rough
Is it a port hole? Does your van have a glass bottom, and in it's previous Australian life, was it semi aquatic and used for taking tourists on boat tours over the Great Barrier Reef?
Good question,,,,, It was an Australia VW thing, its a deeper battery tray, if you look through the hole there is a bolt you put a socket on it and it clamps the battery, so not that exciting but unusual ,,,,, arguably
