My favorite gyms are the ones from Unova. Their obstacles were very challenging, in my opinion. ^^" Anyway, if I were to have a gym, then it'd be gigantic. It would be completely dark there. Every time you defeat a trainer in the gym, one of the lights will lit up and lead you to the next trainer. My team would consist of dark-type Pokémon only, and they'd be Zoroark, Weavile, Shiftry, Spiritomb, Houndoom, and Drapion.