快!There is a ____ in our school.It is flat.We can see many children in it.We have PE lessons in it

快!There is a ____ in our school.It is flat.We can see many children in it.We have PE lessons in it
We can play basketball in it.
到底是什么？flat的意思是平坦，可操场不平坦啊~~我觉得应该是gym体操房~~