Remember the place where you enabled the fans (one room from the top, four rooms from the left)? Just keep going left from there (one room down and maybe three or four rooms to the left). You should find an entrance to the caves. It will lead you directly to the shoes.
If you need further help, here's a map of the "outside part", where I have circled the places where you should go and in which order.
(in hindsight I should have made the game's internal map more useful, but I started implementing it a bit too late and it was hard to put any meaningful info there in that point)