Ant Tunnel, especially if you like training in the wee hours of the morning. Get a party and train together - cover the whole map. I partied with 2 Clerics and 3 other guys and the EXP gained at the bottom right-hand corner never stopped coming.
At LV 35, go to The Burning Zone. It rocks. flaming rocks. One big fat piee of flat land with barbequed pork running at you. The best place for an archer.