The Arrivals Lounges at Barajas are open to all arriving passengers for free (airport charges ignored)! It's open to everyone actually . Read further...

We learned that first hand three weeks ago when we flew business class from ATL. When you claim your luggage and exit the carousels area you will find yourself in the public area full of signs saying Arrival Lounge that way and this way pointing in opposite directions. We looked for that mysterious Arrival Lounge for quite a while asking Information desk (who barely speak any English) and other airport staff. The fifth or sixth person we met spoke a descent English and told us that we have been effectively enjoying the lounge already ever since we left the luggage claim area... Looks like in Spanish or Barajas signs-specific version of English Arrivals Lounge is the same as Arrivals Hall