Puerto Vallarta, Mexico - Princess Cruises celebrates its 50th anniversary this week with a trip down memory lane for passengers. Guests on Pacific Princess will follow the exact route of the cruise line's original 400-passenger Princess Patricia's maiden voyage on December 3, 1965, from Los Angeles to the Mexican Riviera.

Princess Patricia's first cruise took those 400 passengers from Los Angeles to Mazatlan in Mexico and on to Puerto Vallarta and Acapulco - the same itinerary the Pacific Princess is sailing to commemorate the 50-year anniversary.

Princess says passengers on the anniversary cruise will be treated to an array of activities and entertainment commemorating half a century of Princess cruises - and they also will be joined by some surprise guests.

Pacific Princess passengers will enjoy menus featuring popular dishes from the past five decades and formal nights including a golden balloon drop. The ship's top deck "Movies Under The Stars" will show The Sound of Music, also 50 years old this year.

Since launching in 1965 with just one ship, Princess Cruises is now the world's third largest cruise line with 18 vessels traveling to more than 330 destinations. The line took off in the 1970s and 1980s in part because of the success of The Love Boat, a top-rated TV show that was set on an earlier version of the Pacific Princess. That ship, which made regular stops in Puerto Vallarta, was dismantled at a scrap yard in Turkey last year.