Hey!

Well, to answer your question the most directly and generically: into a mass grave, alongside their body. However this of course depended on who you were, and where you were.

I'd also like to challenge that "17,000" number. I see that on Wikipedia, without a source; that number seem high if we're JUST talking about guillontining deaths from 1793-1794 (the timeframe from the Wikipedia article), but low if we're talking total deaths for that year.

Any death statistics for the French Revolution always come down to the details. For example: Over 100,000 people died in the Vendée in 1793; should we include them in the death counts? What about those executed during the Terror, but not by guillotine? The numbers can vary widely depending upon which subset you're looking at (and usually the Vendée deaths are kept separate), so keep that in mind.

Back to the question of where these victims made their final resting place: most non-unique victims of the guillotine were dumped into mass graves. Guillotine victims in larger cities were usually dispatched in batches every day, so say 30 victims would be executed, taken to a mass grave, and uncerimoniously dumped in-- the revolutionaries weren't concerned with proper funery rites.

Something to keep in mind though was that many victims of the Terror were not guillotined: there were many special cases where other methods were employed. Often this comes down to morbid efficiency; during the "Great Terror" (late 1793- July 1794), as the "Representitives on Mission" (National Convention members given full powers and sent out into the departments to enact a governmental presence) attempted to quell various counter-revolution activity and uprisings, there often was neither the time nor inclination to use the guillotine, a rather slow method of executing large groups of prisoners. To highlight a few infamous examples, there was Collot d'Buois, a sans-culotte Committee member who had a large group of political prisoners in Lyons shot with a canon before a mass grave. The most infamous example is John Baptiste Carrier, who tied his unlucky constituents of Nantes together, put them on sinkable barges, and drown them in the Loire river. This is to say nothing of the rebellion ongoing in the Vendée, where republican troops were massacring citizens with military weaponry. I will point out here for anyone interested that this uneven application of the Terror-- and the gruesome methods carried out by men like Collot and Carrier-- was unacceptable to Robespierre, who wished for an even application of what he considered revolutionary justice. He believed that these men damaged the revolution by their excesses, in an equal yet opposite way from those whose leniency let go many committed counter revolutionaries. His attempt to recall and try men like Collot and Carrier (and their permissive counterparts such as Taillen) was a huge impetus for the Thermidorian reaction that brought him down-- lead as it was by the men mentioned above.

Aside from your geographic location, what happened to your corpse depended on who you were. The main instance of this was the former head and body of Louis XVI, who after being executed had his body covered with corrosive materials so that it would dissolve, leaving nothing behind for any sympathetic grave-diggers.

Let me know if you have any more questions!