More than 3,500 business leaders and government officials have flocked to Saudi Arabia for a conference dubbed "Davos in the Desert."

Attendees were hungry for insights on where the major oil producer is headed. They were not disappointed.

Here are four of the biggest takeaways from the summit in Riyadh:

The crown prince

Crown Prince Mohammed bin Salman, the driving force behind sweeping economic changes in Saudi Arabia, made a rare appearance at the conference, addressing a huge audience of investors on Tuesday.

The young crown prince had a message: We are open for business.

He also delivered a warning to ultraconservatives, vowing to to destroy "extremist ideologies" and return to "a more moderate Islam."

"We want to lead normal lives, lives where our religion and our traditions translate into tolerance, so that we coexist with the world and become part of the development of the world," he said.

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It's a development that was welcomed by investors.

Colony Capital chief executive Tom Barrack, who lived in the kingdom in the 1970s, said that these reforms may succeed where others failed.

"His approach is definitively the right one," Barrack said of the crown prince.

"What you've seen here in the last few days is a real commitment of tolerance," he added. "We are going to create an environment for the West that will be transparent, secure, stable and understandable."

A new mega-city

The crown prince also unveiled NEOM, a $500 billion mega-city that will span three countries. The city will be powered entirely by regenerative energy, while also making use of automated driving technology and passenger drones. Wireless hi-speed internet will be free.

Should it become reality, the development could become a major driver of tourism, an industry that is key to the crown prince's ambitious Vision 2030 program. The goal is to diversify the country's revenue and reduce what he once called an "addiction" to oil.

It would also build stronger ties with neighbors Jordan and Egypt, whose territory would be included in the project.

One major caveat: Saudi has previously announced several economic cities that have failed to attract the right investment, with many office spaces reduced to empty caverns in the desert.

Massive investment

Much of the change in Saudi Arabia is being funded by the country's Public Investment Fund (PIF).

The sovereign fund has contributed $45 billion to Softbank's Vision Fund, which is the world's largest technology investor. PIF has also poured $20 billion into a Blackstone infrastructure fund.

Some fund managers and business titans attending the conference have privately expressed worries over the kingdom's ability to deliver on all of the projects built into Vision 2030.

But the pace of new initiatives has only accelerated. On Wednesday, PIF said it plans to increase its assets under management to $400 billion by 2020. It wants to create 20,000 direct jobs and 256,000 jobs in construction.

"I'm sure they need and should be looking at domestic investments as well," said Joshua Friedman, co-CEO of Canyon Partners, "As they interact with the most sophisticated investors globally ... I'm sure they'll bring that sophistication to bear on their own markets."

Related: The man leading Saudi Arabia's overhaul just got more powerful

The world's biggest IPO

One of the biggest remaining questions surrounds a partial sell-off of the kingdom's crown jewel, Saudi Aramco. Officials have said they expect the IPO to value the giant sate oil company at around $2 trillion. If the market agrees, selling just 5% would raise $100 billion.

The debut has been scheduled for 2018, but there are doubts over its realization. Aramco has disputed recent media reports suggesting uncertainty.

CEO Amin Nasser told CNNMoney in an interview that an IPO is on track for 2018, but he refused to define whether it will have an international listing.

"We looked at the different venues, which are New York, London, Hong Kong, Tokyo," he said. "We are taking time for the shareholders [the ruling family] to look at all the data ... and then the decision where to list ... will come in due course."

Economic regulation, foreign ownership laws, and strict Islamic laws have often deterred investors in the past.

This time, investors are listening.