Saudi Arabia has embarked on a grand experiment—a Middle East version of “if you build it, they will come.” Facing an existential threat to oil, the country’s lifeblood, Saudi Arabia is spending more than $3.2 trillion to transform its economy by 2030. While oil remains essential, the country is trying to fashion itself as a high-tech hub and destination for global business and leisure, preparing for the end of the fossil fuel era.