My Dad bought a building in the late 70's, it was coming up on a 100 years old. Rubble stone foundation and what I can only describe to people not near the Niagara escarpment as somewhat water smoothed limestone slabs as the basement floor. They were rough hewn about 3' x 4' each with a uneven surface that had nooks and crannies up to 1" deep all over them.
The basement was chock full of 90 years of accumulated junk including mountains of wood tossed down there after every remodel. After emptying it out, my 14 yo eyes saw a dirt floor with some rocks sticking out of it here and there. My Dad smiled and handed me the two shop vacs we had found in the piles and said to get to work. One worked decent. I filled that 20 gallon vac up 20 or 30 times sucking up the sifted dirt and dust of nearly a century.