tavat sutalam adhyastam
yad adhayo vyadhayas ca
klamas tandra parabhavah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Until Bali Maharaja achieves the position of King of heaven, he shall live on the planet Sutala, which was made by Visvakarma according to My order. Because it is especially protected by Me, it is free from mental and bodily miseries, fatigue, dizziness, defeat and all other disturbances. Bali Maharaja, you may now go live there peacefully.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Visvakarma is the engineer or architect for the palatial buildings in the heavenly planets. Therefore, since he was engaged to construct the residential quarters of Bali Maharaja, the buildings and palaces on the planet Sutala must at least equal those on the heavenly planets. A further advantage of this place designed for Bali Maharaja was that he would not be disturbed by any outward calamity. Moreover, he would not be disturbed by mental or bodily miseries. These are all extraordinary features of the planet Sutala, where Bali Maharaja would live.
In the Vedic literatures we find descriptions of many different planets where there are many, many palaces, hundreds and thousands of times better than those of which we have experience on this planet earth. When we speak of palaces, this naturally includes the idea of great cities and towns. Unfortunately, when modern scientists try to explore other planets they see nothing but rocks and sand. Of course, they may go on their frivolous excursions, but the students of the Vedic literature will never believe them or give them any credit for exploring other planets.