Oslo occupies an arc of land at the northernmost end of the Oslofjord. The fjord, which is nearly bisected by the Nesodden peninsula opposite Oslo, lies to the south; in all other directions Oslo is surrounded by green hills and mountains. There are 40 islands within the city limits, the largest being Malmøya (), and scores more around the Oslofjord. Oslo has 343 lakes, the largest being Maridalsvannet (). This is also a main source of drinking water for large parts of Oslo.