During the reign of Christian IV between 1588 and 1648, Copenhagen had dramatic growth as a city. On his initiative at the beginning of the 17th century, two important buildings were completed on Slotsholmen: the Tøjhus Arsenal and Børsen, the stock exchange. To foster international trade, the East India Company was founded in 1616. To the east of the city, inspired by Dutch planning, the king developed the district of Christianshavn with canals and ramparts. It was initially intended to be a fortified trading centre but ultimately became part of Copenhagen. Christian IV also sponsored an array of ambitious building projects including Rosenborg Slot and the Rundetårn. In 1658–59, the city withstood a siege by the Swedes under Charles X and successfully repelled a major assault.