It is now the core of the Warmian-Masurian Voivodeship. It has about 4,500 km2 and 350,000 inhabitants. Its biggest city is Olsztyn, and the historical capital was Lidzbark Warmiński; another large town is Braniewo. Important landmarks include the cathedral in Frombork, where Nicolaus Copernicus elaborated the heliocentric theory, and sanctuary in Gietrzwałd, a site of Marian apparitions and miracles. It is an area of many lakes and lies at the upper Łyna river and on the right bank of Pasłęka, stretching in the northwest to the Vistula Bay.
Warmia is part of the historical province of Prussia and has traditionally strong connections with Masuria, but it remained Catholic and belonged to Poland before 1772. Warmia has been under the dominion of various states over the course of its history, most notably the Old Prussians, the Teutonic Knights, the Kingdom of Poland and the Kingdom of Prussia. The history of the region is closely connected to that of the Archbishopric of Warmia (formerly, Duchy of Warmia). The region is associated with the Prussian tribe, the Warmians, who settled in an approximate area. According to folk etymology, Warmia is named after the legendary Prussian chief Warmo, and Ermland derives from his widow Erma.
The first traces of human settlement in the region come from roughly 14 to 15 thousand years ago: traces of settlements made by the Lusatian culture (thirteenth—fifth century BC), including above-ground water housings and artificial islands. By the early Middle Ages the Warmians, an Old Prussian tribe, inhabited the area.
In the 13th century the area became a battleground in the Northern Crusades. Having failed to gather an expedition against Palestine, Pope Innocent III resolved in 1207 to organize a new crusade; beginning in 1209, he called for crusades against the Albigenses, against the Almohad dynasty of Spain (1213), and, also around that time, against the pagans of Prussia. The first Bishop of Prussia, Christian of Oliva, was commissioned in 1209 to convert the Prussians, at the request of Konrad I of Masovia (duke from 1194 to 1247).
In 1226 Duke Konrad I of Masovia invited the Teutonic Knights to Christianize the pagan Prussians. He supplied the Teutonic Order and allowed the usage of Chełmno Land (Culmerland) as a base for the knights. They had the task of establishing secure borders between Masovia and the Prussians, with the assumption that conquered territories would become part of Masovia. The Order waited until they received official authorisation from the Empire, which Emperor Frederick II granted by issuing the Golden Bull of Rimini (March 1226). The papal Golden Bull of Rieti from Pope Gregory IX in 1234 confirmed the grant, although Konrad of Masovia never recognized the rights of the Order to rule Prussia. Later, the Knights were accused of forging these land grants.