I am not sure which area you are referring to, but there are a number of situations where what look like walls would go up before an actual floor slab is poured. My first inclination would be a stem wall style foundation where grade is more than a few inches lower than the actual floor.Interesting to me is that there is no poured floor (yet?) for the lowest level of the show building. @Tom is this common? I would think it would need something for moisture control, although perhaps not concrete.