First Class - Explore: Plith, Goblin Fort, Olaria, Kalandor
Second Class - Explore: Reza, Aeth, Pyramid
Third Class - Explore: Achaeus, DV, Tundra
Fourth Class - Explore: Bottle, Lartin Castle, Roadhouse Inn, POA, Varhkans Temple, Mordrakes Tower.
Each Explore <area> quest can have a set number of locations to visit within that area to help you better learn the area. Now since each class has numerous quests like this. Maybe upon completing all the Explore <area> quests within a class you can get a big bonus for doing all those quests within your class. Just an idea.
I know I probably missed some areas and I am sure everyone can probably think of something to add to this so post it!