What attraction, located on Heart Island, was built by the G. W. & W. D. Hewitt architectural firm?
G. W. &amp; W. D. Hewitt: G. W. & W. D. Hewitt was a prominent architectural firm in the eastern United States at the turn of the twentieth century. G. W. &amp; W. D. Hewitt:  The firm specialized in churches, hotels and palatial residences, especially crenelated mansions such as Maybrook (1881), Druim Moir (1885–86) and Boldt Castle (1900–04). Boldt Castle:  It is located on Heart Island in the Saint Lawrence River.
Boldt Castle