Letohrádek Ostrov is situated in the middle of the Chateau Park. The early Baroque summer palace was built between 1673 and 1679 for Julius Francis, Duke of Saxe-Lauenburg, on the site of an earlier wooden pavilion.

Today, it houses a branch of the Karlovy Vary Art Gallery, presenting mainly Czech art from the first half of the 20th century and organising temporary exhibitions, workshops and accompanying cultural events. With a capacity of approximately 30 to 40 people, the venue is suitable for intimate meetings, presentations, workshops and creative programmes.

Events can be combined with a visit to the current exhibition or with activities in the Chateau Park. Regular public events include the Garden Festival, Historical Picnic and Art Symposium. The building is open seasonally from May to October and is not wheelchair accessible.