Duchess of Plaisance Mansion, Protected neoclassical mansion in central Athens, Greece

The Duchess of Plaisance Mansion, or Villa Ilissia, is a complex of four buildings arranged around a courtyard on Vasilissis Sofias Avenue. The central two-storey residence, clad in white marble, has arcades of seven arches on the courtyard side and two corner towers holding the staircases. A fountain and two tall cypresses stand in the courtyard, and the name ILISSIA is carved into the marble arch of the entrance passage.

Sophie de Marbois settled permanently in Athens in 1837, after her daughter's early death, and bought large plots of land. After her first house on Piraeus Street was destroyed, she commissioned Stamatios Kleanthis to build this mansion on the then Kifisias road, now Vasilissis Sofias Avenue. Construction began in 1840 and lasted eight years; she moved in on its completion in 1848 and lived there until 1854. The complex later housed the Evelpidon military school for three years and other military services, and since 1930 has held the Byzantine and Christian Museum.

The mansion now houses the Byzantine and Christian Museum, displaying collections that represent medieval Greek artistic traditions. The rooms contain works reflecting the religious and daily life of earlier periods.

The complex stands on Vasilissis Sofias Avenue, about 600 metres from the former royal palace, now the Parliament. Entry to the courtyard is through a small arcade on the ground floor of a two-storey building; the marble arch above it is carved with the name ILISSIA. The four buildings are grouped around a courtyard with a fountain and two tall cypresses.

The marble arch over the entrance from Vasilissis Sofias Avenue carries the name ILISSIA carved at its apex, a reminder that the Duchess named the house for the nearby Ilissos river. The courtyard it opens onto holds a fountain and two tall cypresses.