San Juan, Metro Manila is 13 times larger than Vatican.
Area: 0 km2 World Factbook
Population: 842 (July 2014) World Factbook
Vatican City, officially Vatican City State, is one of the last six remaining absolute monarchies whose territory consists of a walled enclave within the city of Rome. It has an area of approximately 44 hectares, and a population of around 840. Wikipedia
Area: 6 km2 calculated
San Juan is a city in the Philippines. It is one of the cities that comprises Metro Manila, the National Capital Region of the Philippines. It is the smallest city in the country in terms of land area. Wikipedia