PURPOSE: To enable maintenance of environment and meeting to multipurpose by a method wherein most of an outer peripheral body is built under ground and a lower bottom part forms a lowermost arena, and an elevating roof is built inside audience seats arranged in a multistage and additionally functioned as a moving arena.

CONSTITUTION: A semiunderground type outer peripheral part body 1 is built, high layer, middle layer, and low layer audience seats 2a, 2b, and 2c are arranged at the inner peripheral part of the outer peripheral part body, and a lower bottom part forms a lowermost arena 3. A roof and moving floor 4 is built inside audience seats and supported by elevation type stays 5, and natural lawn are planted on an upper surface to form a moving part arena 7. At a usual period, the floor 4 is positioned at the top part of the body 1 and harmonized with a surrounding park. The floor 4 is moved in a highmost position, where necessary, to form a baseball field, and is lowered among the audience seats to use the arenas 3 and 7 for various events. This structure properly copes with surrounding environment and effectively utilizes a space.