The Botanical Garden covers an area of about 16,000 sq m to 75 m s.l.m., partly on soils of volcanic origin (Roman lavas) and partly alluvial; the climate is subumid thermomediterranean (732 mm average annual rainfall, average annual temperature 18 C).
The area is divided into Hortus Generalis (13,000 m2), which collects mainly exotic plants, and the Hortus Siculus (3000 sqm), intended for the cultivation of spontaneous Sicilian species.
The Hortus Generalis, or formal style, is divided by orthogonal boulevards in twenty-two geometric areas delimited by large stone steps cut limestone; the regularity of shape is accentuated by the presence of three circular tanks, used for the cultivation of aquatic plants.
The Hortus Siculus, with his collection of wild plants on the island, is a peculiar industry. A recent renovation has enabled the creation of diversified areas in which were played some typical Mediterranean environments (dune environment, rock gardens, humid, forest and maquis). In these environments, along with common plants and widespread species are extremely rare in Sicily.