Designed by Alexander Jackson Davis, the five-story rotunda was made of blue-gray stone that was quarried on the island.

After restoration, it has now been incorporated into the adjacent buildings to create a large apartment complex.

Mistreatment of patients at the asylum was the center of the exposé by Nellie Bly in her 1887 book Ten Days in a Mad-House.

In April 2006, after restoration, the renovated Octagon reopened as the lobby entrance to a pair of adjacent apartment buildings with 500 units in total.

In 2006, a newly constructed residential building was built on the site, modeled on the original structure.