San Francisco, officially the City and County of San Francisco, is a cultural, commercial, and financial center of Northern California. San Francisco is the 16th most populous city in the United States, and the fourth most populous in California, with 881,549 residents as of 2019. It covers an area of about 46.89 square miles (121.4 km2), mostly at the north end of the San Francisco Peninsula in the San Francisco Bay Area, making it the second most densely populated large U.S. city, and the fifth most densely populated U.S. county, behind only four of the five New York City boroughs.

Singapore is a sovereign island city-state in maritime Southeast Asia. It lies off the southern tip of the Malay Peninsula, bordering the Straits of Malacca to the west, the Riau Islands to the south, and the South China Sea to the east. The country's territory is composed of one main island and 63 satellite islands and islets. It has the second greatest population density in the world.