Tallinn, Estonia is the capital city and main seaport and has a population of approximately 500,000 people. It is a city with a long history, and can trace its population back nearly 3,500 years. The new, modern, city center is only a short walk from the castles of the past, so tourists can enjoy the treasures of ancient and modern history and sightseeing adventures. The largest lake is the city's main source of drinking water. The only significant river is located in the suburbs of the city. The river valley is protected because of its natural beauty. A limestone cliff runs through the city, and is exposed in a few areas. Historically, Tallinn has been attack on several occasions. Extensively bombed during World War II, the medieval aspect of the city has remained. Tallinn Old Town has become a UNESCO World Cultural Heritage site. In addition to speaking the native Estonia languages, other residents speak and understand Finnish, Russian and English. Estonia is home to the Tallinn Pedagogical University [now called Tallinn University], Estonia Academy of Music, Estonia Academy of Art, Estonian Academy of State Defense, Estonian Evangelical Lutheran Church, and Estonian Business School. Local tourist offices sell Tallinn Cards which offer free access to public transportation and entry to most attractions. Walking tours also offer guides to navigating the city