Las Noches

Las Noches in 'Bleach'
Las Noches is the capital city of Hueco Mundo and where the only palace or fortress located in Hueco Mundo can be found. It is the location where Aizen resides after leaving Soul Society and gives his orders to his Arrancar army, the Espada. The palace is equipped with medical facilities and detention wings. The strongest Hollows are usually found here.

Las Noches in 'Legend of Bleach'
Las Noches is the capital of the Hollow world (in LoB) and the home for Arrancars and, obviously, Hollows. Here, as an Arrancar, you are able to test yourself skill-wise against various Espada as you level.