Monaco, officially the Principality of Monaco, is a sovereign city-state and microstate on the French Riviera in Western Europe. It is bordered by France to the north, east, west and by the Mediterranean Sea to the south. With an area of 2.1 km2 (0.81 sq mi), it is the second smallest sovereign state in the world, after Vatican City. Its 19,009 inhabitants per square kilometre (49,230/sq mi) make it the most densely-populated sovereign state in the world.

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.