Located in the northeastern corner of the Retiro Park, near the O’Donnell gate, it was designed by the architect Isidro Velázquez to create a viewpoint in El Reservado. It is formed of an internal hemispherical vault made of brickwork supported by walls of the same type and covered by a layer of earth that serves as substratum for pine and cedar plantations. It has a small artificial watercourse and features waterfalls and steeply sloping paths to the top which, located at a height of twelve metres, becomes a privileged observation point in the corner of the Retiro. The interior has recently been refurbished to serve as an exhibition hall.