The Il Caloggio WWF Oasis is located in the Municipality of Bollate in the province of Milan, in the southernmost reaches of Groane Park.
The area covers approximately 7 hectares where the Nirone stream flows, the natural watercourse with the cleanest waters between the Ticino and the Adda. The Oasis is accessible from a bridge that crosses the banks of a small canal, a secondary branch of the Villoresi canal.
A fundamental feature of this Oasis is its incredible biodiversity. The vegetation on the banks of the canal includes alders, willows and Pallon May trees. The central part of the Oasis is characterised by the reforestation of oak, hornbeam and elm trees. This environment, rich in insects and seeds of wild grasses, is a popular feeding ground for birds such as sparrows, goldfinches, greenfinches, swallows, redstarts, flycatchers, shrikes, red woodpeckers and titmice. Tree frogs find shelter in the soil during the summer months and flock to the pond to breed.
The Oasis also serves as a habitat for pheasants, rabbits, hedgehogs, weasels and other mammals. The Novera aquatic fauna, which is quite rare for the waterways of Groane, includes bleak and chub fish, along with amphibians such as green frogs, Emerald green toads and newts.
The Oasis also hosts an area known as the "butterfly garden", particularly rich in nectarine plants, highly prized by insects.