TIL there's a secure underground tunnel for celebrities to get to the Oscars

(Kevin Nealon interviews his wife) https://youtu.be/hV6mNEaoTWY Time stamp 7:06

I mean I've always subconsciously figured there must be some secret secure method of conveyance for celebrities to get around clandestinely & safely but nobody ever talks about it because it's secret and now I'm curious to know where the entrance and exits are for these tunnels.