Once located on the south side of Rosneath Bay overlooking the Gare Loch, Rosneath Castle was demolished in 1961 and its grounds now form a park, with facilities for camping and caravans.
Originally the property of the Lennox family, the lands were confiscated by the Crown in the 15th century and given to the Campbell Earls of Argyll. They built or rebuilt Rosneath Castle in the 16th century and it became their second home after Inveraray. The castle was modernised and extended for Archibald Campbell, the 3rd Duke (1682 - 1761), by William (1689 - 1748) and John Adam (1721-92), and later Robert Mylne (1733 - 1811) advised on further enhancements. Consumed by fire in 1802, a new mansion was quickly planned by Edinburgh artist Alexander Nasmyth (1758 - 1840), but the final design an execution fell to London-based architect Joseph Bonomi. Completed in 1806, this grand Neo-Classical mansion presented fine facades to the north and south. It was used as a military hospital during the First World War and was home to Princess Louise, Dowager Duchess of Argyll, until her death in 1939. Thereafter the estates were sold and the house provided a headquarters for the Rosneath Naval base during the World War II. The house was then abandoned and, in 1947, it met the same fate as its predecessor.
A number of associated buildings remain, including the Home Farm by Nasmyth and a grotto possibly built by William Adam or Mylne.
