 Peninsula House and the former observatory sit on a site located close to Windsor on high ground, which, when the river (Hawkesbury) floods, becomes a secluded, unspoilt island, filled with native plants and fauna and protected from development.Peninsula House is a two-storey Georgian style house of sandstock brick.The main roof and verandah are slate, the latter supported on delicate cast iron columns, the centre bay marked with a simple pediment.