Tallinna Lauluväljak (Tallinn Song Festival Grounds)

From www.laulupidu.ee:

One of Tallinn's most worthwhile places to visit is located at the foot of the Lasnamägi area of the city on Pirita Road near the sea. This place is the Tallinn Song Festival Grounds where the All-Estonian Song Festivals have been held since 1928. Also festive ceremonies, concerts, open-air performances, exhibitions, and other events take place in this vast area. In 1988 several manifestations abounding with people were organized where patriotic songs were sung and blue-black-white flags were flown after a lengthy time of them being forbidden. These summer days were later called the "singing revolution". At the end of the summer, on September 11, a huge event took place at the Tallinn Song Festival Grounds entitled "The Song Of Estonia". More than 300,000 people participated, and for the first time the re-establishment of Estonia's independence was openly demanded.
Lauluväljak

The most dominant feature of the Tallinn Song Festival Grounds is the Song festival stage - the only one of its kind. The current grandstand-like sounding board structure, which holds up to 24,000 singers, was erected in place of the previous one for the 1960 All-Estonian Song Festival. The construction of the song festival stage is original and unique. The space between the point of support of the front arch is 73 meters. The back arch unites with it at the same points. In between the two arches is the concavo-convex screen made out of wooden shields, which has two convexities - a hyperboloid paraboloid. This way, all the groups of voices can be distinguished but the sound as a whole is directed out to the Song Festival Grounds.

The width of the song festival stage is 120 meters. The 43 steps of the center section rise 18 meters high. The height of the center of the front arch is 36 meters and its diameter is 2 meters. Both of the side walls of the song festival stage reach out to the towers. During the festival, radio and television broadcasts can be made from the south tower. At the top of the 42-meter-high north tower is the festival flame. The building materials of these structures include locally mixed limestone, concrete, wood, and metal. The creators of the project (A. Kotli and H. Sepmann, architects; E. Paalman, engineer; H. Laul and H. Oruvee, consultants) were successful in designing an architectural masterpiece that is whole and unique. This includes a concavity in the shape of an ellipse which is where the audience sits. This area is 200 meters in length and 175 meters in width.