Santa's workshop

plural Santa's workshops

1. The mythical structure, usually envisioned as located at the North Pole, where Santa Claus and a large number of capable elves work tirelessly and gladly year-round to produce all of the toys and other gifts to be delivered throughout the world on Christmas Day.
2. A fanciful replica of this structure, temporarily erected in a retail store, shopping mall, or other public venue at Christmastime as an attraction for children and parents.
3. broadlyidiomaticA busy, productive large or small work environment, populated by dedicated workers.

   Like a Santa's workshop for the rich, the huge shopping atrium was jammed with frenzied workers pushing to finish by Monday's opening.

   1983 February 11, Robin Herman, Laurie Johnston, “Frenzied Finish For Trump Tower Atrium”, in New York Times, retrieved 15 May 2014

   3 more examples

   An acid-tongued blonde who writes a legal-affairs column for the right-wing weekly Human Events, Ann Coulter . . . laughed. "There are lots of us busy elves working away in Santa's workshop."

   1999 February 21, Michael Isikoff, “The Right Wing Web”, in Newsweek, retrieved 15 May 2014

   U.S. consumers . . . will look to China, as they have since the country a decade ago became a regular Santa's workshop for toys, clothes and electronic gizmos.

   2001 January 8, Aparisim Gosh, “Trapped in the System”, in Time, retrieved 15 May 2014

   Next week 500 books not shipped elsewhere directly from the printer will arrive at our house. . . . At that point my Brooklyn brownstone will turn into Santa’s workshop as I package courtesy copies for all the sources who helped and people whose photos appear in the book. I will also send out review copies.

   2012 June 13, Deborah L. Jacobs, “How My Book Became A (Self-Published) Best Seller”, in Forbes, retrieved 15 May 2014

   Synonyms: hive of activity