Lake Rotorua is the second largest lake in the North Island of New Zealand, and covers 80 km2. It is located at in the Bay of Plenty region 50 kilometres south of Tauranga. The city of Rotorua is sited on its southern shore, and the town of Ngongotaha is at the western edge of the lake.
The lake was formed from the crater of a large volcano in the Taupo Volcanic Zone. Its last major eruption was about 140,000 years ago. After the eruption, the magma chamber underneath the volcano collapsed. The circular depression left behind is the Rotorua Caldera, which is the site of the lake. Several other lakes of volcanic origin are located nearby to the east, around the base of the active volcano Mount Tarawera.
A chain of three lakes (Rotoiti, Rotoehu and Rotoma) are located to the northeast of Lake Rotorua. Lakes Rotorua and Rotoiti are connected by a small channel, and both drain to the Bay of Plenty via the Kaituna River.
Mokoia Island, close to the centre of the lake, is a rhyolite dome. It is probably New Zealand's best-known lake island, and is closely associated with one of the best-known Maori legends, that of Hinemoa and Tutanekai.
Owing to the geothermal activity around the lake (including still active geysers and hot mud pools), the lake has a high sulphur content. This gives the lake's waters an unusual yellowish-green hue.
