With a population of about 45,000, Hilo is the largest census-designated place, and the largest settlement on the Island of Hawaii. Two volcanoes shield the Hilo Bay: Mauna Loa, an active volcano, and Mauna Kea, a dormant volcano. In fact, this area is home to one of the most important astronomical observatories. Today, human settlements stretch from Hilo Bay to Waiākea-Uka. The first inhabitants of the area brought many Polynesian traditions with them. Eventually, the city expanded due to the introduction of sugar plantations to the area. With a tropical rainforest climate, the city is the third wettest in the United States.