Vishnupurana 2.7.20

2.7.20

kṛtakākṛtayor madhye maharloka iti smṛtaḥ
śūnyo bhavati kalpānte yo 'tyantaṃ na vinaśyati //

Wherever earthy substance exists, which may be traversed by the feet, that constitutes the sphere of the earth, the dimensions of which I have already recounted to you. The region that extends from the earth to the sun, in which the Siddhas and other celestial beings move, is the atmospheric sphere, which also I have described. The interval between the sun and Dhruva, extending fourteen hundred thousand leagues, is called by those who are acquainted with the system of the universe the heavenly sphere. These three spheres are termed transitory: the three highest, Jana, Tapa, and Satya, are styled durable: Maharloka, as situated between the two, has also a mixed character; for although it is deserted at the end of the Kalpa, it is not destroyed. These seven spheres, together with the Pátálas, forming the extent of the whole world, I have thus, Maitreya, explained to you.