Moldova is one of the smallest and least populous countries in Europe, with a population of around 4 million people within an area of 33,846 square kilometers. It was formerly part of the Russian Empire in 1812 and later reunited with Romania in 1918 before becoming part of the Soviet Union in 1940 following the Molotov-Ribbentrop Pact. Moldova declared independence from the USSR in 1991. Some of Moldova's notable features include over 40 parks, the 8th largest cave in the world, its capital city which was once known as the "Little Paris of Europe", and historical sites such as 30 monasteries and churches dating back to the 15th century.