Consider the Venetian, which already ranks as the sixth-biggest hotel in the world and the fourth largest in Las Vegas, home to 15 of the 20 largest on the planet. This colossus will assume the top spot once it opens a 3,200-suite tower, now under construction, that will bring its room count to more than 7,000.

Another development, Echelon Place, will have more than 5,000 rooms when it is built on the site of the old Stardust, which its owners demolished last month. The MGM currently ranks as the largest hotel in Las Vegas — and the world — with 5,000 rooms.

At $4.4 billion, Echelon Place would rank as the most expensive development in Las Vegas history — if not for the $7 billion the MGM Mirage is spending on CityCenter. That price is far more than the previous record, set when Wynn and his financial backers spent $2.7 billion building the 2,700-room Wynn, which opened in 2005.

Even competitors marvel at the scope of the CityCenter project, which MGM calls the most expensive privately financed project in American history. This minicity bordering the Las Vegas Strip will feature six towering buildings that reach as high as 61 stories. Covering 67 acres, it will include a 4,000-room hotel, a sprawling convention center, a half million square feet of retail space and 2,700 condominium units.

The changing demographics have led the designers of the new Vegas to push a sleek and modern aesthetic, along with amenities like luxurious spas, in place of the gilt and gaudy properties that reigned in the 1980s and 1990s. But their owners' ambitions are greater than ever.

"The building we're seeing right now," said Gary Loveman, chief executive of Harrah's, which operates half a dozen casinos on the Las Vegas strip, "is by leaps and bounds bigger than anything we've ever seen."

For a long time, Harrah's had only one major casino in Las Vegas. "One of my predecessors was convinced in the late 1980s, early 1990s, that Las Vegas was overbuilt," Loveman said. "That turned out to be a wrong call. Spectacularly wrong."

Even more than hotel construction, a boom in condominium development has increased the number of construction cranes crowding the skies.

Developers, including Donald J. Trump and Florida-based Turnberry Associates, are collectively spending billions of dollars building condo towers on or near the Strip, adding thousands of units even as the local real estate market, like much of the country, has been mired in a downturn.

But MGM and other developers see themselves as competing for buyers far beyond the Las Vegas market. "We see these as third homes," said Alan M. Feldman, a spokesman for MGM.

Data provided by the National Association of Realtors indicated that the median price of a condo in the Las Vegas metropolitan area fell by 3 percent in the second half of 2006.