The former main building of madrid’s central train station “atocha” is tranformed into the waiting hall. the new part of “estación de madrid atocha”-where the trains depart- is not really worth seeing. unless you wanna take a train somewhere. the you should go there.
otherwise just stay in the waiting hall. it’s a perfect place to relax. not only while waiting for your train but also during sightseeing because some of the big museums (like prado or reina sofia) are quiet near. it hosts shops, cafes and a botanic garden. and a pond with hunderds of turtles. and who doesn’t love watching turtles, while they’re doing, well, nothing.