Connecticut’s Department of Energy and Environmental Protection is opening the historic Gillette Castle in East Haddam for the holidays. The 24-room home built by the actor William Gillette will be decorated in the style of 1914, when construction began. The castle will be open 10 a.m. to 4 p.m. on Saturdays and Sundays, from Nov. 29 through Dec. 21. Santa and Mrs. Claus will be on hand from noon to 3 p.m. Local entertainment will take place on selected days and free hot chocolate and warm cider will be available. The grounds of the Gillette Castle State Park, which abut the Connecticut River, are open daily year round. The state acquired the property in 1943.