World famous One Tree Hill, U2 wrote a song about it, stands at the centre of Cornwall Park, a landscaped European-style park and working farm in Greenlane. Sir John Logan Campbell, a prominent Aucklander gifted the park to the people of New Zealand in 1901 when he realised that Auckland's suburbs were spreading at an alarming rate. In 1841, Campbell built the first house in Auckland, Acacia Cottage which still survives today. Originally sited in what is now downtown Auckland, it was shifted to the park in the 1920s. Campbell is buried on the summit of One Tree Hill.

The 125 hectare farm at Cornwall Park is unusual in being located in the middle of a busy urban area. Sheep and cattle are farmed and lambs are a common sight during the spring.

There are over 20 resident bird species in the park, native species such as Grey Warbler, Fantail and Tui are common, as are colourful exotic species such as Rosellas, Welcome Swallows and Goldfinches. Kaka, Native Pigeon and Paradise Shelduck have also be sighted in the park. There are many gardens with beautiful flowers located throughout the park and many of the trees are 150 years old.