Go to veilstone city. Then go down to route 214 until you get to VALOR LAKEFRONT. Once you leave the grassy area turn left towards the indent with a shade under a tree, go into there and you'll get to lake valor.
How Do I Get To Lake Valor In Platinum?
First you fly to Pastoria city. Then you go on route 213 until you come to a small town.You head in direction of Veilstone city.When you exit the town and are on the green part of ground ,walk 15 steps forward. Then walk 18 steps to left .Then you will be at lake Valor.
