Here's a list of locations in the Fire Nation with a brief summary on them.
*Boiling Rock A large prison with many guards and high security. Most important criminals and war prisoners are sent here.
*Capital City The capital of the Fire Nation. It is assumed to be the highest populated city in the Fire Nation, and is the home of Firelord Ozai and the Fire Sage Council. There is a royal palace for the Firelord as well.
*Jang Hui Village A small village built in the Jang Hui River as a fishing place. The river was polluted by a nearby Fire Nation Factory, until it was destroyed.
*Shu Jing Village A small village in a mountain region on the Fire Nation mainland. It is seen to have many waterfalls, and is the home of swordsman Piandao.
*Ember Island An island off the coast of the continential Fire Nation. Has sandy beaches, and many estates, one of which is owned by Ozai.
*Roku's Island A small uninhabited island with a dormant volcano on it. It is known to be Avatar Roku's old home, until it was destroyed by a volcanic eruption.
*Fire Fountain City A large industrial city, mainly for production of weaponry. There is also a population of villagers and much commerce.