religious Order. The Order had been created in Acre (present-day Israel). When this last stronghold of the Crusades fell to Muslim Arabs, the Order moved its headquarters to Venice before arriving in Prussia. Malbork became more and more important in the aftermath of the Teutonic Knights' conquest of Gdańsk (Danzig) and Eastern Pomerania in 1308. The Order's administrative centre was moved to Marienburg from Elbing (now Elbląg). The Grand Master of the Teutonic Knights, Siegfried von Feuchtwangen, who arrived in Marienburg from Venice, undertook the next phase of the fortress' construction. In 1309, in the wake of the papal persecution of the Knights Templar and the Teutonic takeover of Danzig, Feuchtwangen relocated his headquarters to the Prussian part of the Order's monastic state. He chose the site of Marienburg conveniently located on the Nogat in the Vistula Delta. As with most cities of the time, the new centre was dependent on water for transportation. The castle was expanded several times to house the growing number of Knights. Soon, it became the largest fortified Gothic building in Europe, on a nearly site. The castle has several subdivisions and numerous layers of defensive walls. It consists of three separate castlesthe High, Middle and Lower Castles, separated by multiple dry moats and towers. The castle once housed approximately 3,000 "brothers in arms". The outermost castle walls enclose , four times the enclosed area of Windsor Castle. The developed part of the property designated as a World Heritage Site is . The favourable position of the castle on the river Nogat allowed easy access by barges and trading ships arriving from the Vistula and the Baltic Sea. During their governance, the Teutonic Knights collected river tolls from passing ships, as did other castles along the rivers. They controlled a monopoly on the trade of amber. When the city became a member of the Hanseatic League, many Hanseatic meetings were held there. [[File:Castillo de Malbork, Polonia, 2013-05-19, DD 41.jpg|thumb|left|View of the High Castle (zamek wysoki') from the west]] In 1361, the future Grand Duke of Lithuania Kęstutis was briefly imprisoned in the castle. In 1365, Polish King Casimir III the Great visited the castle. In the summer of 1410, the castle was besieged following the Order's defeat by the armies of Władysław II Jagiełło and Vytautas the Great (Witold) at the Battle of Grunwald. Heinrich von Plauen successfully led the defence in the Siege of