The Zuyderzee was a large inland sea located in the northern part of the Netherlands. It was connected to the North Sea and played a significant role in the region's fishing and shipping industries. Over time, the Zuyderzee became less practical due to flooding and land reclamation efforts. In the 20th century, the Zuyderzee was transformed into the IJsselmeer, a large freshwater lake, through the construction of the Afsluitdijk, a major dam. This project aimed to protect the surrounding land from flooding and to create new agricultural land, significantly altering the landscape and economy of the area.