Everest gets the lion’s share of media coverage, but alpinists know that K2 —  at 8,611 meters, the second-highest peak in the world — is more challenging. Perhaps those difficult conditions explain why there are so few documentaries about K2, but K2: Siren of the Himalayas tells the story of a 2009 ascent of the mountain by Fabrizio Zangrilli and Gerlinde Kaltenbrunner, a century after the Duke of Abruzzi’s famous expedition. Filmed in Pakistan, this often-gripping documentary shows how hard it is for even the world’s finest alpinists to climb this mountain, where for every four people who have reached summit, one has died trying.