A Pa is a fortified settlement, By recording the earthworks, almost 7,000 pre-European Pa sites have been identified throughout New Zealand, mostly in the north of the North Island. It has been shown that these fortified sites began to be built about 1500 AD, 250 years after Maori first arrived in New Zealand. Very few palisades (fences) remain but defensive ditches and banks are characteristic of most pas. Also scarps may have been created to steepen slopes. Flat terraces were places where gardening (horticulture) took place and houses were sited. After the introduction of the musket the form of pas was modified. These pas are referred to as Gunfighter Pas. The pa sites are the earliest examples of man's contribution to the New Zealand landscape.