The Legion's Gym is where the Legionnaires train and hone theirs skills. It's also a magical place where the Legion lads seem to always be shirtless! Much to the delight of fangirls (and some fanboys) everywhere.
Ultra Boy & Mon-El spar in black speedoes! From Secret Orgins #42.
Invisible Kid cools off after a dip in the pool. From Legion of Super HeroesVol. 3 #42
Shirtless Colossal Boy... and pantsless Sun Boy! From Legion of Super Heroes Vol. 3 #46.