I always get this one wrong, too, using "dans" instead of "aux". I guess one just has to memorize this? Sometimes it's "en", sometimes "dans," sometimes "aux." Oh la la. Merci.
'il existe' does not work? i thought i could be used instead of 'il y a'. it make ssense if 'il existe' is used to refer to something existing but i learned earlier on from the tree it can be used to point something out physicially