In the film "The Hangover", where do the four friends travel for a bachelor party?

The Hangover is a 2009 American comedy film directed by Todd Phillips, co-produced with Daniel Goldberg, and written by Jon Lucas and Scott Moore. It is the first instalment in The Hangover trilogy. The film stars Bradley Cooper, Ed Helms, Zach Galifianakis, Heather Graham, Justin Bartha, Ken Jeong, and Jeffrey Tambor.

It tells the story of Phil Wenneck, Stu Price, Alan Garner, and Doug Billings, who travel to Las Vegas for a bachelor party to celebrate Doug's impending marriage. However, Phil, Stu, and Alan wake up with Doug missing and no memory of the previous night's events and must find the groom before the wedding can take place.

The Hangover was released on June 5, 2009, and was a critical and commercial success. The film became the tenth-highest-grossing film of 2009, with a worldwide gross of over $467 million. The film won the Golden Globe Award for Best Motion Picture – Musical or Comedy, and received multiple other accolades. It is the tenth-highest-grossing worldwide film of 2009, as well as the second-highest-grossing R-rated comedy ever in the United States, surpassing a record previously held by Beverly Hills Cop for almost 25 years.