New series from National Geographic Channel promise to take viewers inside intriguing places, from Roswell, N.M., to J. Edgar Hoover’s closet.

Nat Geo, now in more than 60 million homes, recorded one of the biggest increases in viewership of any cable network in 2006, up 14 percent among total viewers during prime time, according to Nielsen Media Research. The new programming is designed to continue building the network’s momentum.

“Everything that we’re doing is cooking,” said Michael Cascio, senior VP of special programming for Nat Geo. Earlier this year, the network made a splash with “The Gospel of Judas,” and its series “Dog Whisperer” has become a part of pop culture, he said, even being lampooned on Comedy Central’s “South Park.”

The new nonfiction shows are in keeping with what the channel has been doing successfully. “We’re taking the core elements of the National Geographic brand and bringing them to life,” Mr. Cascio said.

Beginning later in the fourth quarter of 2006 is a series tentatively titled “Undercover History.” The show looks at some of modern history’s most familiar conspiracy theories. For example, the show will look at which conventional-wisdom factoids about former FBI director J. Edgar Hoover are true and which are not. Another episode will try to tell where Amelia Earhart vanished. The series will also look closely at the supposed UFO landing in Roswell, N.M.

“Undercover History” will be vetted to National Geographic’s scientific standards, Mr. Cascio said. Whether it produces a body, alien or otherwise, “You’ll have to tune in to find out,” he said.

In the second quarter, National Geographic will televise “Situation Critical,” which looks at key moments in newsworthy events, such as the near-disaster on Apollo 13 to the North Hollywood bank robbery and shootout in 1997.

The series builds off the channel’s “Seconds From Disaster” series, but Mr. Cascio said that “Critical” is more “dramatic,” while “Disaster” is more “analytical.”

The network has also ordered six more episodes of its series “Hunter and Hunted,” which looks at incidents of animal violence toward man.

National Geographic is also working on two upcoming specials, one titled “Winter,” which features information on the effects of cold and answers such questions as “What makes ice slippery?” The other, “Summer,” examines heat and other seasonal phenomena such as why fireflies light up, how ice cream melts and why sunscreen works.