If you are on your way to Nimbasa City from Castelia City then in the sand place go to the left and follow the trail. When you get to a clearing, go straight and you can enter the castle. This is one of my favorite places because in the basement you can catch a Volcarona and I caught mine with a Dive Ball! Don't try it, it's hard. I was trying to use a Timer Ball.
there is a backpacker in relic castle who will give you either a plume fossil (which is revived into an archen) or a cover fossil (which is revived into a tirtouga)
at the end of it
Volcarona is inside Relic Castle.
It's in the Agate village and is close (left to and below) the Pokemon center
The Relic Castle is on route 4 where you have to go left and then up again.
Relic Castle
Relic Castle
Desert Resort.
you don't "pass" relic castle you go to it later and meet team plasma (you also get a fossil if you talk to the backpacker!)
By trade.
if you go down to the very bottom of the relic castle go up the all the stairs and you should be out. hope this helps! =)
there is a backpacker in relic castle who will give you either a plume fossil (which is revived into an archen) or a cover fossil (which is revived into a tirtouga)
relic castle
team plasma does
in the desert resort
route 4 or relic castle
at the relic castle