On Pokemon Diamond and Pearl where is a good place to train my Luxray?

I have a Luxray on Level 42 on Pokemon Diamond. I train it at the restaurant at Valor Lakefront everyday. But where else can I train it? By the way, I've completed the game, so I have access to most areas.|||Route 222 use vs seeker (all guys have water Pokemon)|||somwhwere with rock pokemon or with others|||U could go to the island where the resort area is and fight against the higher level pokemon. thats what i always do. or go onto wifi and try to go up against people. or the battletower. =D