In 1929 Chester Thordarson built this boathouse with help from Frederick Dinkelberg, a noted Chicago architect, to design the limestone monolith; Thordarson served as his own general contractor. The structure was anchored to bedrock seven feet below the water’s surface. All the stone – in fact, almost all the building materials, except the red tile roof that weighs 50 tons – came from the island. The lower level of the boathouse can accommodate two 50-foot yachts. Atop it, rising 65 feet above the water, is the 40′ x 70′ architectural wonder that Thordarson called his Jewel House of Art and Nature. Thordarson’s boathouse has been deemed one of the most historically significant buildings in the state, it is also listed on the National Register of Historic Places.