Lake Eyre (pronounced "air") is the lowest point in Australia, at about 15 m (49 ft) below sea level. When it fills with water, it is the largest lake in Australia, being 144 km (89 mi) long and 77 km (48 mi) wide. It is also in the driest part of Australia, getting only about 100 mm (4 in) of rain each year. It is in the north of South Australia, about 700 km (435 mi) north of Adelaide. The lake was named after the explorer, Edward Eyre, who was the first Europen to see it in 1840. It is the centre of the Lake Eyre National Park.