Mbh 2.11.1a

“Narada said,--Listen to me, O child, as I tell thee of the assembly house of the Grandsire, that house which none can describe, saying it is such. In the Krita (golden) age of old, O king, the exalted deity Aditya (once) came down from heaven into the world of men. Having seen before the assembly-house of Brahma the Self-created, Aditya was cheerfully wandering over the Earth in human form, desirous of beholding what could be seen here. It was on that occasion, O son of Pandu, that the god of day spoke unto me, O bull of the Bharata race, of that celestial Sabha (assembly) of the Grandsire, immeasurable and immaterial and indescribable, as regards form and shape, and capable of delighting the heart of every creature by its splendour. Hearing, O bull of the Bharata race, of the merits of that Sabha, I became, O king, desirous of beholding it. I then asked Aditya, saying,--O exalted one, I desire to behold the sacred Sabha of the Grandsire. O lord of light, tell me, O exalted one, by what ascetic penances, or by what acts, or by what charms or by what rites, I may be enabled to behold that excellent sin-cleaning Sabha.”--Hearing these words of mine, Aditya the god of day, the deity of a thousand rays, answered me, O chief of the Bharata race, thus: Observe thou, with mind rapt in meditation, the Brahma vow extending for a thousand years. Repairing then to the breast of the Himavat, I commenced that great vow, and after I had completed it the exalted and sinless deity Surya endued with great energy, and knowing no fatigue, took me with him to the Sabha of the Grandsire. O king, it is impossible to describe that Sabha, saying--it is such, for within a moment it assumes a different form that language fails to paint. O Bharata, it is impossible to indicate its dimensions or shape. I never saw anything like it before. Ever contributing to the happiness of those within it, its atmosphere is neither cold nor warm.