Musty odor

I have a split entry ranch home. There is a crawl space under the floor of the foyer that retains a musty odor.
The area not heated or normally open to the rest of the house. There is an access panel at the back of a coat closet on the basement level. The floor of the area is basement level. The outside wall is concrete block and attached to it is a dirt filled concrete block and concrete capped porch landing.
There is no evidence of water intrusion but I'm sure that there is some moisture from condensation. I have been considering venting it by opening up a hole in the wall between it and the garage and installing a small fan.
Any suggestions?
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