Thousand fold world system
31 planes of existence coming together is one universe. In each universe there is a Maha Brahma in each Brahma plane.


  ... a thousand brahmā worlds. ...


According to the Abhidhamma there are infinite world systems. See: Abhidharmartha Pradipika By Amaradasa Rathnapala.

Also see: The Buddhist Concept of World by Bhikkhu T. Seelananda and also this answer.