|...the inner castle|
You can see the tavern at the bottom, the place where you can hire experienced heroes. At the right sight is the wizards tower. In there your heroes can train their magic abilities. But you can also brew some potions, which will help your heroes in the dungeons.
At the left is the barrack, the right place to train the strength. The archery at the top of the picture is also for training, and guess for what... for dexterity ;)
Every of these buildings can (and should) be upgraded to provide better results in training.
The gate on the top guides you to the castle, where you can hire unexperienced heroes from your soldiers. The advantages of these are, that you can determine what class they should be (warrior, archer or wizard), they didn't cost anything and you can customize their equipment, which is not possible for heroes you hire in the tavern, which are like mercenaries. And yes, you have to pay them every day, and the better they get, the more expensive they are.