Batcave

The Batcave is the secret headquarters of Batman, (Bruce Wayne), consisting of a series of subterranean caves beneath his residence, Wayne Manor.

Young Justice
The Batcave was first introduced in the episode "Downtime" while the Young Justice team went to their homes. While Robin was training presumably in Wayne Manor, a glimpse of the cave was viewed with Batman watching on the monitor. This marks the first appearence of Alfred Pennyworth as well.