The museum's tiered roof gardens (26,400 square feet) were designed by landscape architect Dan Kiley, working with Geraldine Knight Scott and the museum architects, Kevin Roche and John Dinkeloo. The gardens opened with the museum, in 1969, to critical and popular acclaim. Rising four levels from the courtyard, they are interspersed with 17 terraces and sculpture beds. The rectilinear composition was determined by the architects; Kiley and Scott worked on the technical and aesthetic aspects of the planting design. Kiley used native and non-native evergreen plants. The structures, in exposed aggregate concrete without natural drainage, required a new technology in the 1960s and are richly planted so that, in Kiley's words, 'architecture and landscape are integral and inextricable' [Dan Kiley in his own words, by Day Kiley and Jane Amidon, Thames and Hudson, London, 1998).