National Geographic Channel has ordered an expanded 10-episode fifth season of “Locked Up Abroad,” the cabler’s highest-rated summer show, as well as a seventh season of “Taboo.”

“Locked Up Abroad” had a combined 7.8 million viewers over its first five episodes, topped by its June 30 premiere, “The Real Midnight Express.” The fifth season will bow in 2011.

Nat Geo also scheduled the seventh-season premiere of “Dog Whisperer With Cesar Milan” for Oct. 8 (with Howie Mandel as guest) and Sundance Film Festival grand jury prize winner “Restrepo” for Nov. 29.

In addition, Nat Geo will present four episodes of “Humanly Impossible II,” while also offering “Ancient X-Files,” a four-parter examining historic mysteries such as the Holy Grail.

Nat Geo specials for the coming season include “Secrets of the Giant Crystal Cave,” “CIA Confidential II” (focused on post-9/11 CIA operations in Pakistan), “Man-Made Disasters,” “Bismarck’s Sinking” and “Ghost Ship,” along with documentaries on former U.S. secretary of state Henry Kissinger and Argentine writer-activist Ariel Dorfman, exiled from New York to Chile during the Red Scare.