Centuries before WWII turned its historical centre into landfill, Elbląg was a stronghold and port of the Teutonic Knights. In the 13th century, the Vistula Lagoon (Zalew Wiślany) extended further south than it does today, allowing the town to develop as a maritime centre and a member of the Hanseatic League. When Elbląg came under Polish rule after the Treaty of Toruń, it was a major gateway to the sea. Later, Swedish invasions and the gradual silting of the waterway capsized the town’s prosperity, though a partial revival came with industrial development in the late 19th century.