Dragon Castle Size

Dragon Castle was three hundred meters wide, a thousand meters long, and was divided into two parts; the Cage, and the tunnels for the monstrous beasts. The Cage was where the life-and-death battles would be carried out, while the beast tunnels were where the monstrous beasts were imprisoned. Because Dragon Castle held many monstrous beasts inside, it was extremely dangerous, which is why it had been built outside of the city.

Book 1, Chapter 15