Where is a good place to level up in Final Fantasy IV (DS)?

Question

I am currently in the underworld, before the sealed cave.

Answer 1

I would level up in the caves that lead to The journey there along is worth EXP, along with the  Sylvan Cave that leads to Yang who was rescued by the Sylphs. I say these caves because there is an enemy here, I cannot quite recall her name, but she looks like an old fat hag. Here, she calls these puppets, or dolls to battle. Only attack the dolls, and she will keep calling them. I did this for hours and when I got bored, I killed her. Each of my characters went up like 6-7 levels due to the EXP I earned. It is the easiest way to level up. Just make sure to cast float so you avoid the lava or whatever it is.