Tucked within an exclusive Key Haven cul-de-sac, Casa di Sempre is a European-inspired waterfront estate offering more than 260 linear feet of water frontage across two sides of the property, including 200 feet of concrete dockage for boating enthusiasts. Resting on over 15,000 square feet of land, this residence showcases superior craftsmanship and thoughtful design throughout more than 6,500 square feet of refined living space. The main residence features five bedrooms and four-and-a-half baths, while a three-bedroom, three-bath guest villa provides privacy and comfort for visitors. Constructed of 11-inch insulated concrete forms with poured concrete floors and stairs, the home provides extraordinary strength, safety, and sound insulation. Impact glass windows and doors are complemented by hidden European-style roll-down shutters, ensuring both security and elegance. Inside, an open gourmet kitchen, formal dining room, study, and three fireplaces create a warm yet sophisticated ambiance. Eight-foot mahogany interior doors and windows elevate each space with timeless craftsmanship. Outdoors, the estate is a true entertainer's haven, highlighted by a 65-foot heated glass-mosaic pool with a 21-foot infinity edge, three cascading waterfalls, and an island with a six-seat swim-up bar leading to a custom cabana. A private 400-square-foot gym and 3,800-square-foot garage complete the amenities, along with a generator and fire suppression system for added peace of mind. A rare combination of elegance, engineering, and waterfront grandeur, Casa di Sempre represents one of the most remarkable estates in the Lower Florida Keys—crafted for those who value strength, sophistication, and sanctuary by the sea.