Dante was drawing on centuries of prophetic visions and vision narratives--the voyage through the otherworld was the single most common type of religious vision in Christianity through 1200 or so, according to Peter Dinzelbacher. (They continued in popularity in and of themselves after that date; however, Christocentric visions associated above all with women mystics skyrocketed in importance).

I've discussed some predecessors of Dante that either develop many of the ideas he will or were his direct influences a couple of times on AH:

• Since most of our physical and visual perceptions of hell come from Dante or later works, what did earlier medieval European Christians associate hell with in a visual or physical sense?
• Dante's Satan is guilty of treason. Milton's Satan falls because of pride. What was Satan's real sin, according to medieval theology? (I know the topic isn't quite the same, but my answer quotes substantially from Mechthild of Magdeburg's vision of hell)