Riyad-us-Saliheen 404
Abu Hurairah (May Allah be pleased with him) reported: We were in the company of Messenger of Allah (PBUH) when we heard a bang. Thereupon Messenger of Allah (PBUH) said. "Do you know what this (sound) is?" We said, "Allah and His Messenger know better." He (PBUH) said, "That is a stone which was thrown into Hell seventy years before and it has just reached its bottom".
[Muslim]
One can imagine the torments and horrors of Hell from its depth.