In Doctor Who, which 2010 episode follows the Doctor into the chamber containing the Pandorica?

In Doctor Who, “The Pandorica Opens” follows the Doctor into the chamber containing the Pandorica.

The episode is the first part of the series-five finale and was written by Steven Moffat. The Eleventh Doctor, Amy Pond, Rory Williams, and River Song investigate the Pandorica, a legendary prison said to contain the universe’s most dangerous being. The episode reveals that the threat is not what the characters initially expect.

It originally aired on BBC One on 19 June 2010. The story continues in “The Big Bang,” which resolves the cliffhanger and concludes the season. The title uses the Pandora myth as a model for a sealed container whose contents may transform the surrounding world.

The episode is sometimes confused with “The Big Bang” because the two stories form a single finale. “The Pandorica Opens” is specifically the opening chapter, ending before the main resolution.