There are certain laws pertaining to a floor. For example, if a Sefer Torah is dropped on the floor, one is supposed to do some sort of atonement (eg., most famously, fasting for 40 days).
What is considered a floor in Halachah? Does an elevated platform have that status? What size? How about a stage - or a Bimah, for that matter? Is a car floor a floor? A bus, train, or airplane? Moving or parked?