The land consists of most of the former agricultural land of Spaniards Farm and Wyldes Farm.
The Heath Extension is bordered on its southern side by Hampstead Way and Wildwood Road, on its eastern side by Wildwood Road, with
the Great Wall enclosing the north-west side.
The most obvious aspect of the Heath Extension is how little it has changed from the former
feld pattern of Wyldes Farm.
The hedgerows are a major landscape feature dividing the large space into a series of green 'rooms', each of which has a distinctive character.
There is a wide variety of habitat on the Heath Extension, including bramble and thistle, hazels and hollies, hawthorn hedges, native black poplar along with fora and habitat for Odonata (dragonfies and damselfies) on the banks of the ponds.
There are many feld trees, for example, elder, feld maple, and good examples of boundary oaks.
Although there are two small sections of tarmac path, the main track running from the southern boundary down to the cluster of maintenance buildings in the centre of the Extension is a roughly gravelled farm track.
Other paths are also lightly gravelled and informal, and the area, although mown, is not manicured;
it is defnitely an open space rather than a park.
The acquisition of the [link:3]Heath Extension[/link:3] was largely the achievement of [link:1]Henrietta Barnett [/link:1](later Dame Henrietta).
She married Samuel Barnett (later Canon Barnett).
The Extension was threatened by the Hampstead tube company, wishing to extend the underground across the Heath.
Dame Henrietta formed the Hampstead Heath Extension Council in 1903.
It's Aim was to purchase 80 acres of [link:2]Wyldes Farm[/link:2], adjoining the Sandy Heath, and then add them to Heath.
The Wyldes Estate belonged to Eton College and The Heath Extension Council but after a great struggle it was purchased.
The remaining 240 acres of Wyldes Estate was bought and eventually became Hampstead Garden Suburb.
At the far end of The heath Extension, between Hampstead Way and North Point is the Great Wall (Unwin's Great Wall), designed by Charles Wade from "early Lutyens".
Unwin was inspired by medieval German towns, particularly Rothenburg in creating this illusion of a "city wall" and its detailed design is derived from Lutyens's garden at Orchards, near Godalming (designed 1897, completed 1900).
The big round-arched entrance to the gardens behind the wall, with their radiating voussoirs of tiles-on-edge, are derived directly from those which flank the kitchen garden at Orchards.
The weather-boarded gazebos are influenced by the Orchards' bothies.
Furthermore, Wade must have observed how Lutyens had himself created a "city wall" at Orchards by means of a raised parapet walk giving views over the surrounding countryside.
Behind the wall a second line of defence is given by the backs (as carefully considered as the fronts) of the large individual houses, the most expensive in the Older Suburb, which form a varied but continuous solid band of horizontal geometry behind which rises Lutyens's great steeple of St. Jude's.