very old house whats under the kitchen tile... woodfloors??
If it's a really old house then yes, there were hardwood floors under there, originally. But there might not be anymore depending on what renovations have been done. That said, if the floor is that much higher than adjoining areas, it's a good bet that they layered it right on top of what was there.
Mike has the right idea. Also, try pulling out the fridge or another appliance as often the floor does not go all the way under them, or they are sitting on plywood that you can pull up to see what's underneath.