stored=null;
  storedLocation=null;

  im1=load("_img/ps/valdavia.gif");
  im2=load("_img/ps/osuna.gif");
  im3=load("_img/ps/piscina.gif");
  im4=load("_img/ps/gimnasio.gif");

  function load(location){
    image=new Image();
    image.src=location;
    return image;
  }
  function show(where,what){
    stored=where;
    storedLocation=document.images[where].src;
    document.images[where].src=eval(what+".src");
  }
  function hide(){
    document.images[stored].src=storedLocation;
  }