ignore directories while using pretty permalinks

i don’t know if i’m not searching hard enough or what, as i’ve seen this question unanswered several times, and have yet to find a solution that works.

how do you get wp to ignore a directory? the root of my wp site is http://www.mysite.com and subsequent pages are permalinked as http://www.mysite.com/about/ and http://www.mysite.com/food/ etc

however, i get a “not found” error when i try to access a physical directory like http://www.mysite.com/gallery/ in which i wish to be independent of my wp install.

how do i get wp to ignore existing directories?