The largest puzzle I’ve ever completed was The Garden of Earthly Delights, a painting by Hieronymus Bosch, 10 000 pieces. It was produced by Educa in 1997, and it was, at the time, the world’s largest puzzle, at least according to the box. According to Rare Puzzles, there is a 9000-piece version available, but the 10 000-piece one is very rare. I still have mine, and I’m not selling 🙂

I bought the puzzle in the late 90s, but it took me more than 10 years to work up the courage to actually assemble it. The pieces were in 5 bags of 2000 each. I didn’t mix the bags and essentially completed five 2000-piece puzzles. I started on November 29th, 2011, and finished on January 12th, 2012. Once I got started, I was amazed at how fast it went.
Unfortunately, I have no pictures of the different stages, just the completed puzzle:

I have every intention of assembling this again one day – and then it will be much more difficult. I did not take it apart in sections, so next time it really will be one 10 000-piece puzzle instead of five 2000-piece ones…