You can find rare Pokemon from other games and even shiny Pokemon! I found a Shiny Hippopotus once :P
Check your PokeDex. All Pokemon which areas are glowing red need the pokeradar to find them.
To get a pokeradar in Pokemon diamond and pearl, you must see all of the sinnoh Pokemon in the game, then go to profeser rowan's lab and talk to him. he will give you a pokeradar and with it you can find Pokemon from other regions.
Route 228.Use PokeRadar.
You need a pokeradar and it will be in route 218
pokeradar is only at Pokemon pearl , diamond and platinum.
on route 230 use your pokeradar
pokeradar is not in FR. it is in Diamond, Pearl, and Platinum
Try using the pokeradar, its not perfect but it could lead you to a find.
you need a rare pokeradar you find it on routes 226 and 225.
You use the Pokeradar in tall grass in Pokemon Pearl version. The grass will shake and show you the location of rarer Pokemon.
Grass will move, walk into grass but it will wear off after a while.
there pretty rare but you can find it with pokeradar on route 218