"The Tower of Nicanor: The King of Lambs" by Francisco Javier Barrera
One thing I love about this OPD is that it serves to ignite the imagination. Listen, I get that this is pretty spartan as far as one page dungeons go. This is often the case with submissions that lean heavily on an illustration or isometric cartography. Barrera did a great job suggesting a lot with the illustration of the tower and the use of simple labels. This was a very popular submission for a reason.