From the Introduction:
Deep underground, unknown to most, lies this treasure vault, protecting countless riches. Even only partially filled, as it is now the amassed wealth hidden here is mind boggling. In some spots the silver and gold coins, making up the majority of the vaults contents, are piled almost chest high. The construction of the vault matches the value of its contents. Floor and stairs leading down to its entrance are tiled with black and white marble and the bricks covering the walls to provide a contrast to the floors and the vaults contents are only covering steel reinforced walls.
A door forged from massive, almost arm thick steel bars is only the first measure barring entrance to the vault. Far more impressive is the massive round steel door sealing the actual entrance. Crafted from a single piece of the best steel this door weighs tons and nothing short of a full grown dragon could move it by force without knowing the secrets of its arcane locking mechanisms. The mind of those learned in the matters of engineering boggles thinking of the massive foundations that must lie below this vault to carry the weight of this door alone, not to mention that of the reinforced walls of the vault.