The scene shown here is Alessandro Botticelli's illustration of Dante's Inferno, Canto XVIII. It is a colored drawing on parchment, 320 x 470 mm, dating from the 1480's and is part of the collection of the Staatliche Museen, Berlin.
The colorful figures you see are Vergil, in blue, the guide to the underworld, and Dante, in red. Here is a brief overview of the scene they are observing, from John D. Sinclair's commentary on the Inferno.
More of these amazingly detailed, accurate, and imaginatively rendered illustrations here.In the first ditch the two trains of panders [pimps--GH] and seducers, circling opposite ways but alike in their betrayal of innocence to lust, are driven by the scourges of horned demons, horns being traditionally associated with adultery, and their sin keeping them in eternal unrest. . . .
The second is the ditch of the flatterers and nothing less than its vile circumstances [they are wallowing around in a pit of excrement--GH] could express the nausea, emphasized by the unusual brevity of his account of it, that is felt by one of Dante's temper for their sin.
http://www.artpassions.net/cgi-bin/dore_image.pl?../galleries/dore/inferno1.jpg
But I should not forget that Sandro was probably moved by the murder of Guiliano de' Medici (Lorenzo's brother) by the Pazzi conspirators in 1478, as they were best buds (per not such factual sources) and it's widely argued that the model for Venus (and the lady in Spring) was Guiliano's girl friend - so maybe 1480s works
ahh, Florence - to be there in the Spring....
P.S. - the bodies that da Vinci drew on the long gallows ropes are the Pazzi conspirators hanging high off the Palazzo della Signoria - he was "using" them to study pendulum motion and anatomy (he had nothing to do with the hanging, just watching) - at least that's the story handed down....