Time Out says
Barangaroo Reserve’s concrete cave is a 5,000-person entertainment space and it’s often used for free events and activations as part of major festivals throughout the year. It’s a space flexible enough to host fashion shows, children’s workshops, music performances and free art installations as part of Sydney Festival. It is located beneath the Stargazer Lawn and above the Barangaroo car park. It’s as long as a cricket ground, as wide as an Olympic swimming pool.