Gringotts Bank is a wizard's bank located in Diagon Alley. It has vaults in tunnels hundreds of miles under London and is run by goblins. Gringotts is known for its tight security and Hagrid notes that "yeh'd be mad ter try an' rob it". There are many spells and enchantments protecting the vaults, as well as dragons that guard the high-security vaults. 
 Known Gringotts Employees
 Engraved Poem on Gringotts Doors
Enter, stranger, but take heed
Of what awaits the sin of greed,
For those who take, but do not earn,
Must pay most dearly in their turn.
So if you seek beneath our floors
A treasure that was never yours,
Thief, you have been warned, beware
Of finding more than treasure there.