Saw a book on rootcellar design in a home steading mag, I'll see later if I can find it.
My relatives had cellars, my folks had storm cellar that was not great, damp & musty, was made of the old tile style blocks (1920's era??)
I suspect this was more storm shelter than for adiquate food storage.
(Cool and Dry)Temprature should be stable, adiquately ventilated, good drainage is evaprative storage
My grandmother had a cellar dug in side of a hill it had a three roll's to play, Cooling short term food storage/ long term storage and tornado shelter(twister belt) on entering the entry door it had a gradual decending arched portico to a main circular chamber, entry was poured concrete with arched ceiling, she had set produce on wood boards off the floor (not direct contact of floor) the entry was wide enough to pass with bushel baskets set all long one side, length was about round 20 feet, then another wood door "tight fitting" into a circular room with domed ceiling ceiling was little over 6 foot tall as my head brushed the top when standing stooped a mite, reminicent of a bomb shelter, had a 6" roof vent pipe and grated floor drain (keep out mice & snakes)had good drain in floor, was sloped for drainage, as I remember ther was a raised bench like ring 8" high and 20 inches deep, round the room with wood shelving for ball jars of canned stuff.
the concrete floor was wetted in the summer (evaprative cooling) on the poritico steps to keep cases of eggs chilled for the egg & cream truck.