This information comes from an interview with former LA Zoo curator Michael Dee who worked in the old zoo area when it was a quarantine area for the current LA Zoo built in 1966 approximately a mile from this site.
I reviewed the Griffith Park Zoo and recounted my visit with Mike here:
http://www.zoochat.com/22/put-me-zoo-review-old-los-314434/
These grottos are sometimes used for movies. They were used in the bear scenes in the movie "Anchorman" with Will Ferrell.
