I just wanted to comment on Pete's answer to Felipe Voloch but it seems I can't so I'll write an answer instead. I think that L'Enseignement Mathématique does publish purely expository papers. I have two examples in mind (hope I'm not mistaken):

• L. Illusie "Catégories dérivées et dualité: travaux de J.-L. Verdier" Enseign. Math. (2) 36 (1990), no. 3-4, 369--391
• J. Nicaise "Formal and rigid geometry: an intuitive introduction and some applications." Enseign. Math. (2) 54 (2008), no. 3-4, 213--249