After defeating Wattson, head west from Mauville City to Verdanturf Town. Here, you can help Wally's uncle clear the Rusturf Tunnel with Rock Smash (HM06). This connects Verdanturf to Rustboro. Then, head north from Mauville City onto Route 111. You'll encounter the Winstrate family, who will challenge you to a series of battles. Continue north through the desert (you'll need the Go-Goggles later to fully explore it) and then east onto Route 112. You'll find the Fiery Path, a volcanic cave. Navigate through it, using Strength (HM04) if you have it, to reach the other side. Continue east through Route 112 and then south through Route 113 (known for its volcanic ash) to Fallarbor Town. From Fallarbor, head south through Route 114 and then east through Jagged Pass to reach Lavaridge Town, home of the fourth Gym.
