A sure sign of summer, or at least summer programming, arrives with “The Adirondacks” (8 p.m., PBS, check local listings), a two-hour meditation on the largest park in the lower 48 states, presented in high definition where available.

For several centuries now, the Adirondacks have been associated with summer and summer camps, particularly the grand resorts for the rich of the Gilded Age and the private “camps” of America’s 19th-century plutocracy, folks with names like Vanderbilt who bought up vast tracts of land and created architecturally notable monuments to their leisure.

While many associate national parks and wilderness with Yellowstone or the vast, remote stretches of Alaska, it’s interesting to note that the 6 million acres of the Adirondack park are located within easy driving distance of New York, Boston and Montreal and constitute the only national park that contains large cities and towns. Lake Placid is among them and has been the host of two Winter Olympics. The Adirondacks are also unique in that the land is evenly split between private property and protected wilderness.

“The Adirondacks” celebrates the artists, rafters, naturalists and woodsmen who call the park home and who try to earn a precarious living in a wilderness resort that some say divides its year into two distinct seasons – winter and the Fourth of July.

¢ “Secrets of the Dead” (7 p.m., PBS, check local listings) unearths new evidence about the sinking of Atlantis, or at least the ancient Minoan civilization associated with the legend of that lost city. “Dead” travels to the Greek island of Santorini, destroyed by the eruption of the volcano Thera in 1600 B.C. Many believe that this same eruption may have created the tsunami that destroyed the Minoans.

¢ The competitors are challenged to “reinvent” the salad on “Top Chef” (9 p.m., Bravo). Call me cynical, but it’s often occurred to me that many of Bravo’s shows, including “Top Chef,” appear to be more about merchandising than cooking. Just last week, Bravo announced several brand extensions for the “Top Chef” concept, including a series of “Top Chef” sea cruises beginning in May 2009 and hosted by former “Top Chef” contestants. In addition to the cruise specials, “Top Chef” will lend its name to a series of classes at the renowned Culinary Institute of America. There will also be a 20-city “Top Chef” tour.

Tonight’s other highlights

¢ The top two face off on the season finale of “America’s Next Top Model” (7 p.m., CW).

¢ Dallas Cowboy Terrell Owens guest stars on “Under One Roof” (7 p.m., MyNetwork).

¢ Tonight’s results show reveals the top two on “American Idol” (8 p.m., Fox).

¢ Scheduled on a two-hour “MythBusters” (8 p.m., Discovery): Hollywood heists.

¢ The documentary “Maxed Out” (8 p.m., Showtime) looks at the growing credit-card debt crisis facing many families.

¢ You can never find a taxi-cab killer when you need one on “CSI: NY” (9 p.m., CBS).

¢ A murder at an auto shop reveals online hanky-panky on “Law & Order” (9 p.m., NBC).

¢ A Denny-for-president movement emerges on “Boston Legal” (9 p.m., ABC).