Afterlife Tours as Genre
Mystical visions of the afterlife were common in the ages of Christendom, and have remained so into the modern age. Numerous holy Christians had visions of Hell and Purgatory: Bede, Boniface, Fursa, Henry Suso, Gertrude, Teresa of Avila, Josefa Menendez, Gemma Galgani, the children at Fatima, and many more. Of course, these stories were spread for the purpose of moral edification rather than literary enjoyment, but it's worth taking a glance at those poets who spun entertaining stories out of these visions and created a literary genre of sorts.
The Voyage of St. Brendan (ca. AD 900), for instance, includes a side trip to the mouth of Hell, where one of his sinful monk-companions is swallowed up, and where they witness the torments of Judas. They eventually find the Country of the Saints before they must return home.
The Irish continued the tradition with the Legend of the Purgatory of St. Patrick (ca. 1180), which tells of a knight named Owein who must descend into Purgatory and witness all manner of terrible sufferings before being purged of his own sins.
Dante's Comedy (composed 1308-20) truly elevated the Journey Through the Afterlife genre into something grand. His depiction of Hell is visceral, and his architecture of Purgatory is surprisingly original. Most visionaries and theologians saw Purgatory as a sort of walled-off section of Hell, but Dante built it as a towering mountain reaching up towards Heaven.
Piers Plowman (ca. 1370) tells a story of many dream visions, some of which include events in the spiritual realms, such as the Harrowing of Hell.
As Christendom diminished, the edifying aspects of this genre began to diminish. Romantic adventure tales often included brief visits to the afterlife, but for comic effect. Milton's Satan in Paradise Lost (1667) is something of an anti-hero, and he is the one taking a self-guided and unedifying tour of the afterlife. C.S. Lewis' The Great Divorce places a dreamer in Hell and Heaven, but muddies the water by making Hell grey and dull rather than a place of clear punishment. In modern literature, any tours of Heaven and Hell are likely to be given ironically and with great secular prejudice.
If anything, this is a genre waiting to be revived in its original Medieval spirit. We still have mystics in the Church who are given visions of the blessed and damned, but few poets who care to make those visions aesthetically pleasing.