In 1529, Warsaw for the first time became the seat of a General Sejm and held that privilege permanently from 1569. The city's rising importance encouraged the construction of a new set of defenses, including the landmark Barbican. Renowned Italian architects were brought to Warsaw to reshape the Royal Castle, the streets and the marketplace, resulting in the Old Town's early Italianate appearance. In 1573, the city gave its name to the Warsaw Confederation which formally established religious freedom in the Polish–Lithuanian Commonwealth. Due to its central location between the Commonwealth's two major cities of Kraków and Vilnius, Warsaw became the capital of the Commonwealth and the Polish Crown when Sigismund III Vasa transferred his royal court in 1596. In the subsequent years the town significantly expanded to the south and westwards. Several private independent districts (''jurydyka'') were the property of aristocrats and the gentry, which they ruled by their own laws. Between 1655 and 1658 the city was besieged and pillaged by the Swedish, Brandenburgian and Transylvanian forces. The conduct of the Great Northern War (1700–1721) also forced Warsaw to pay heavy tributes to the invading armies.