New Zealand's North Island is perhaps best known for the unique volcanic plateau at its centre, with active volcanoes and magnificent examples of geysers, boiling mud pools, hot springs and steam vents. Other popular attractions include the Waitomo Caves, with their underground rivers and glittering glow worms, not forgetting the historic Bay of Islands − one of New Zealand's most beautiful marine parks, offering diving, swimming with the dolphins, sandy beaches and historic villages. There are also four national parks, including a World Heritage Site, thermal fields, hot springs, ski areas, native forest, rivers and historic Maori sites. The country's capital, Wellington, is known as the 'Cultural Capital' for its wealth of theatre, music and art. But, the largest city is Auckland which is known for its cosmopolitan ambience, vibrant Pacific culture and stunning harbours − there are more boats per capita here than any other city in the world.