The last Gym is in Sunyshore City.
In Sunnyshore city same as pearl/diamond.
The sixth gym is in Canalave City of Pokemon Pearl, west of Jubilife City.
go to the Pokemon league
the light house is at the last city you go to where the lightning type gym is.=)
at the sunny shore gym
SunyShore City It is the last gym, so stock up on Ground Moves or whatever. :D
The 6th Gym Leader in Pearl is Byron who is in Canalave City.
snowpoint city
in eterna city
pastoria city
You go north from the city and face the elite four basically
you beat the gym leader