The Collaborative International Dictionary of English v.0.48:

Rincon \Rin*con"\, n.; pl. Rincones. [Sp. rinc['o]n.]
   An interior corner; a nook; hence, an angular recess or
   hollow bend in a mountain, river, cliff, or the like.
   [Western & Southern U. S.] --D. S. Jordan.
   [Webster 1913 Suppl.]