Gillette Castle State Park is located in East Haddam, Connecticut. The park features the unique Gillette Castle, built in the early 20th century by actor and playwright William Gillette, famous for his portrayal of Sherlock Holmes. The castle is known for its distinctive architectural style, resembling a medieval fortress, and is surrounded by scenic woodlands and trails. Visitors to the park can explore the castle's interior, which showcases original furnishings and intricate stonework. The park also offers hiking trails, picnic areas, and beautiful views of the Connecticut River, making it a popular destination for outdoor enthusiasts and history buffs alike.