It's rebooting a Michael Crichton original
In 1972, Crichton wrote a screenplay for the very first Westworld. The late scribe's story revolved around a more complex park, known as Delos, that actually comprised three destinations: Western World, Roman World, and Medieval World. All were as self-explanatory as they sound, with bots that served the same purposes as those mentioned above.
In Crichton's version, which he directed, two Delos patrons (Richard Benjamin and James Brolin) visit Westworld just as a mysterious technological "virus" makes its high-tech inhabitants (namely Yul Brynner's black-hatted gunslinger) go rogue. The resulting monsters-run-amok movie, in which humans pay for dominating their mech counterparts, plays as equal parts gripping action thriller, behavioral evaluation, and old Hollywood homage.
MGM was the only major studio that wanted Westworld, greenlighting a $1.25 million budget and six-week shoot. With VFX sleight of hand, original stunts, camera-cutting, and luck, Crichton and his team delivered a tight flick that ran under 90 minutes and earned an unexpected 95% approval rating after previews.