Now where else are you going to spend $200,000 and get a house that boasts a rooftop patio, offers a panoramic view of the Atlantic and can withstand a direct hit from a destroyer? A steal, no? Nevertheless, Don Cappelletti has had his home on the market for four months and has yet to strike a deal.

Maybe prospective buyers object to climbing a few steps—like 117. The house in question is a 90-foot-high observation tower, without an elevator, erected by the Army Corps of Engineers during World War II to look for enemy submarines. A private investigator, Cappelletti, 51, first spotted the tower in 1978 while driving along the coast southeast of Boston. "I fell in love with it the minute I saw it," says the Boston native, who paid $35,000 for the reinforced concrete monolith in Marshfield, Mass.

Cappelletti and his wife, Ann, spent their summers in the 12-foot by 12-foot, nine-room, eight-story structure, which Ann calls "Don's vertical ranch." It was not "my prized possession," says Ann, 51, a science teacher. "Every time we turned around, tourists were knocking on the door wanting to climb the tower or use the bathroom. I felt like we should open a lemonade stand."

There were a few other drawbacks. The tower has few windows and only one bathroom, on the ground floor. When he arrives, Cappelletti says, he makes sure he has everything before climbing to the fourth-floor bedroom or sixth-floor living room, "because you hate to have forgotten something once you've gone up."

Now Don and Ann live on Cape Cod in a horizontal ranch house, but Cappelletti still thinks his beloved tower has fabulous potential. "It could be fixed up real glamorously," he says. "I see it as a luxury bachelor pad, like something in a magazine." He may be losing altitude, but his hopes remain high.