Rancho Cucamonga, California is 4.9 times larger than Nauru.
Area: 21 km2 World Factbook
Population: 9,488 (July 2014) World Factbook
Nauru, officially the Republic of Nauru and formerly known as Pleasant Island, is an island country in Micronesia in the South Pacific. Its nearest neighbour is Banaba Island in Kiribati, 300 kilometres to the east. Wikipedia
Area: 104 km2 calculated
Rancho Cucamonga is a suburban city in San Bernardino County, California. As of 2014, Rancho Cucamonga's population was 165,775 people.Since 2000, it has had a population growth of 29.53 percent. L. Dennis Michael was elected as the city's mayor on November 2, 2010. Wikipedia