One of Southwest Florida's most extraordinary riverfront estates, 3836 Harold Avenue brings the romance of historic Palm Beach architecture to a private, gated setting in Old Fort Myers. Inspired by Addison Mizner's Mediterranean Revival style and designed inside and out by David Naylor, this one-of-a-kind residence pairs timeless artistry with reinforced-concrete construction, deep-water boating, and a Caloosahatchee River setting. Built in 2012, the home offers approximately 8,701 square feet of air-conditioned living space, five bedrooms, five full baths, and three half baths. Enter through custom doors into a Spanish-inspired courtyard with covered walkways, balconies, and two working fountains adorned with handmade, hand-painted Mizner Industries tile. Beyond, a breathtaking great room rises approximately 30 feet beneath a Cypress ceiling and massive beams. An immense, independently engineered wall of impact-resistant glass frames the pool and river, filling the room with light and connecting it to the waterfront. Imported Italian limestone floors, a Francois & Co. limestone fireplace and custom kitchen range hood, hand-carved doors, intricate millwork, and artisan-crafted details give the home authenticity. The kitchen, family spaces and riverfront terraces flow beautifully for everyday living and grand entertaining. A private, approximately 1,500-square-foot first-floor owner's retreat includes separate dressing and bathing areas, a steam shower, fitness space, and direct garage access. Upstairs are multiple en-suite bedrooms, a private sitting area, a guest suite with its own exterior entrance, a river-view office with carved “Romeo and Juliet” doors, and a richly paneled Irish pub and media room opening to a riverfront balcony. A second office is on the main level. The substance behind the beauty is equally compelling: poured reinforced-concrete structural walls extend through both levels, with pre-stressed concrete slabs forming the second floor. PGT impact-rated windows and doors, specialized engineering for the monumental glass enclosure, and spray-foam attic insulation reflect a residence conceived for strength, comfort, and longevity. Outdoors, covered Cypress-ceiling terraces, a full kitchen and bar, pool and spa overlook the river. A new custom dock with composite decking, two lift positions and direct Caloosahatchee access makes this a rare offering for serious boaters. An oversized four-car garage, integrated home automation, multi-zone audio, lighting and security complete the estate. Just off historic McGregor Boulevard, near downtown Fort Myers, the Edison and Ford Winter Estates and Donald Ross-designed Fort Myers Country Club, this property offers privacy near the city. Its scale is impressive; its warmth is unexpected. Its craftsmanship, engineering, waterfront setting, and singular design place 3836 Harold Avenue among the most distinctive estates in Southwest Florida.