Egholm Off the northwestern side of the city in the sound is the island of Egholm, reached via ferry. The island, with a population of 55 , covers an area of and consists mainly of farmland although there are still a few untilled areas of salt marshes and woodland. Dikes have been built along the coastline to protect the island from flooding. The Kronborg Forest on the island, covering an area of , was acquired by the municipal government in 1945. A restaurant in the vicinity was established in 1918 but rebuilt in 1946 following a fire. To the west of Egholm is the smaller uninhabited Fruensholm, and there are also three small islands to the north. Lakes and chalk deposits There are several man-made lakes nearby: Lindholm Kridtgrav lies to the northwest of Skanse Park on the northern side of Limfjord, while Nordens Kridtgrav to the northwest of Mølleparken is on the southern side. The Aalborg area is one of three in Denmark where chalk deposits are found (the others being Møns Klint and Stevns). The largest quarry is at Rørdal in Øster Sundby ( to the east of the city centre), while Vokslev ( to the west) has also provided chalk. Clay is also quarried in Østerådalen in the southern outskirts, making the area ideal for cement production. Parks and green spaces The Østre Anlæg park is one of the oldest in Aalborg, visited by up to 175,000 people a year. It was used as a dumping ground in the 1920s before being cleaned up and made into a recreational area in the 1930s and 1940s. It contains lawns, flowers, tall trees, bushes, and a lake, overlooked by St. Mark's Church on the eastern side. The lake is on the site of a former clay pit. Fifty-one species of bird have been recorded in the park. Lindholm Fjordpark, to the south of the Lindholm's industrial park, forms part of the green sector of the city known as 'Ryåkilen' along the coast of the sound, covering roughly . Like Østre Anlæg, it once served as a waste site with landfill, and a housing estate was built on its northeastern side. Its use as a landfill site was gradually discontinued in the 1990s, and in 1996, extensive restoration work began. Today it has woodlands and open areas with grass and herbaceous vegetation, notably buckthorn. It is also a habitat for