Saturnalia

Like the achievement description says, you will need to find and light all the bonfires that are located around Gravoi. This should be fairly easy to accomplish as you explore the various buildings and stores around Gravoi. Make sure you have a good number of matches and use the maps or Anita to travel to the different corners of the city. You should pass by most of the bonfires naturally doing this. As a note of caution, the bonfires will be reset if you get a game over by losing all your characters, but as long as they are all lit at the same time at at least one point, you will get this achievement.