Cameron Diaz and beau Alex Rodriguez are welcoming 2011 in Las Vegas, RadarOnline.com has learned.

PHOTOS: Cameron Diaz & A-Rod Live The Good Life In Mexico

After spending a week in Cabo San Lucas, and then making brief pit stops at their respective homes -- she in L.A., he in SoBe -- the couple landed in Vegas Thursday to celebrate the opening of The Cosmopolitan of Las Vegas, a $4 billion resort.  That's billion with a B!

The Cosmopolitan is opening this weekend with Coldplay and Jay-Z performing at an over-the-top New Year's Eve bash, and we expect to see Gwyneth Paltrow and Beyonce there with their mates.

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Cam and A-Rod will be front and center for the lavish event.  They got the party started early with a visit to the Sugar Factory on Thursday.

Las Vegas seems to be THE place to be New Year's Eve.  Sporting her new fabulous cornrow look, Kim Kardashian is hosting a party at Tao Las Vegas.

PHOTOS: Kim Kardashian Sports New Look

Also in Vegas are Ludacris, Diddy and Rihanna. Diddy will host a celebration at Luxor's LAX while Rihanna will be front and center at Las Vegas' PURE Nightclub. Ludacris is leading the countdown to 2011 at a party at Vanity.

Newly engaged LeAnn Rimes and Eddie Cibrian are getting set to welcome in the new year in Cabo San Lucas. The couple has put in hours of beach time – with LeAnn wearing one tiny bikini after another.  When we caught up with them on Thursday, they were scouting out locations for a New Year’s Eve party with their friends.

PHOTOS:  LeAnn Rimes & Eddie Cibrian In Cabo

Paris Hilton is also ringing in the new year in Cabo. Friday morning the heiress Tweeted: "Another beautiful day in Cabo, Mexico. Having the best time! Is everyone excited for New Years Eve?"

In Los Angeles, David Arquette and Jeff Beacher will give us a sneak performance of Beacher's Madhouse at The Hollywood Roosevelt. Their vaudeville-inspired show includes outrageous circus acts and animals.

And in Berlin, David Hasselhoff will be performing before the legendary Brandenberg Gate.  They love the Hoff in Germany!

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