Olympics, the sailing (then known as yachting) events were held at Pirita, north-east of central Tallinn. Many buildings, such as the Tallinn TV Tower, "Olümpia" hotel, the new Main Post Office building, and the Regatta Centre, were built for the Olympics. In 1991, the independent democratic Estonian nation was restored and a period of quick development as a modern European capital ensued. Tallinn became the capital of a de facto independent country once again on 20 August 1991. The Old Town became a World Heritage Site in 1997, and the city hosted the 2002 Eurovision Song Contest. Tallinn was the 2011 European Capital of Culture, and is the 2023 European Green Capital Award. The city has pledged to cut greenhouse gas emissions by 40% by 2030 and takes pride in its biodiversity and high air quality. But critics say that the award was received on false promises since it won the title with its "15-minute city" concept, according to which key facilities and services should be accessible within a 15-minute walk or bike ride but the concept was left out of the green capital program and other parts of the 12 million euro program amount to a collection of temporary and one-off projects without any structural and lasting changes. Geography Tallinn is situated on the southern coast of the Gulf of Finland, in north-western Estonia. The largest lake in Tallinn is Lake Ülemiste (), which serves as the main source of the city's drinking water. Lake Harku is the second-largest lake within the borders of Tallinn and its area is . The only significant river in Tallinn nowadays is the Pirita River, in the eponymous Pirita city district. Historically, a smaller river, called Härjapea, flowed from Lake Ülemiste through the town into the sea, but the river was diverted into underground sewerage system in the 1930s and has since completely disappeared from the cityscape. References to it still remain in the street names Jõe (from jõgi, river) and Kivisilla (from kivi sild, stone bridge). A limestone cliff runs through the city. It can be seen at Toompea, Lasnamäe, and Astangu. However, Toompea is not a part of the cliff, but a separate hill. The highest point in Tallinn, at 64 m (about 200 ft) above sea level, is situated in Hiiu, Nõmme District, in the south-west of the city. The length of the coast is . It comprises three bigger