Explaining the Holy Verse: And hell is made to appear on that day. On that day shall man be mindful, and what shall being mindful (then) avail him? (89:23)
The Holy Prophet is reported to have said, "On the Day of Resurrection, hell will be brought forth in such a manner that it will have a thousand bridles and every bridle will be held by a thousand angels. Thus a million angels will be dragging hell. Hell will be shrieking and flames will be leaping high from it. It will encircle the entire gathering in Mahshar like the bezel of a ring. People of hell will be so restless that some of them will be almost dead. At that time will come the Command of God to bring forth Sirat. A bridge will be raised over hell and each and everyone will have to pass over it without any exception. The following verses (Surah Maryam 19:71-72) explain this matter :
And there is not one of you but shall come to it; this is, an unavoidable decree of your Lord
And We will deliver those who guarded (against evil), and We will leave the unjust therein on their knees.
Both the people of paradise and the people of hell will have to cross that bridge. Then the Holy Prophet said, "There will be seven valleys in that path and there will be some stations in every valley and every station will be of a length of seventeen thousand farsakhs (1 farsakh=6 km) and seventy thousand angles will be posted in every valley. All will have to cross all of these valleys compulsorily."
Adapted from the book: "The Hereafter (Ma'aad)" by: "Ayatullah Dastghaib Shiraazi"