Where in Nacrene city do you find Archen and Tirtouga?

In Nacrene City, you can find Archen and Tirtouga in the Dreamyard, a location accessible after you obtain the first gym badge. Specifically, Archen can be found by using a hidden item or encountering it in the area, while Tirtouga is available as a reward for players who choose to revive fossils at the appropriate location in the game.