The presented area of northern Mazovia is located in central Poland and administratively from 1998 r. covers a significant part of the province. Masovian (without the ends of the south-east. and south) and small fragments of the province. Warmian-Masurian Voivodeship, Podlasie and Kuyavian-Pomeranian. In total, it has over 20000 km2, i.e.. ok. 6,5% country area. This area is inhabited by approx. 3,4 min residents, i.e.. ok. 9,5% the country's population. More than 2,4 min residents live in cities. The largest city is Warsaw – the capital of Poland, having a surface 495 km2 and counting over 1625 thousand. residents (data from the end of June 1997 r.). Other cities are larger in terms of the number of inhabitants, although much smaller than Warsaw, is Płock (130,5 thousand), Ostrołęka (54,8 thousand), Pruszków (53,1 thousand), Legionowo (50,8 thousand), Otwock (44,3 thousand), Ciechanów (47,2 thousand), Sochaczew (39,9 thousand), Wolomin (36,6 thousand), Mława (30,5 thousand), Piaseczno (25,8 thousand), Nowy Dwór Mazowiecki (27,5 thousand), Grodzisk Mazowiecki (25,1 thousand), Wyszków (25,8 thousand), Plonsk (22,9 thousand) and Ostrów Mazowiecka (22,5 thousand). Currently, in terms of nationality, these areas are almost exclusively inhabited by Poles. Only in some resorts (Brands, Mława) small groups of Gypsies and Roma live. In the past, Jews also lived here (especially in cities and larger villages), as well as Russians and Germans. In terms of denominations, the faithful of the Roman Catholic Church dominate. Locally, the Mariavites form large clusters (currently belonging to two religious associations), Evangelicals (Evangelical-Augsburg Church, Evangelical Reformed and Evangelical Methodist), Baptists, Orthodox, Jehovah's witnesses, Jews and others. In the past, the Mennonites present in the Vistula area were an interesting religious group.