When 39-year-old Cabletron co-founder Robert Levine retired in 1997, newspapers called him “eccentric” — he did, after all, wear ostrich-skin boots and chase off a pizza delivery boy in his armored tank, as he told it — but he was just getting started. The mansion has an indoor and an outdoor shooting range. “You never really even have to leave the estate to have fun. I don’t know of another place like it,” The 25,000-square-foot recreation center called “the Lodge” includes a five-story rock climbing wall, an elevator, an indoor shooting range, a teppanyaki (similar to Hibachi) dining area, a...