Long before satellites or GPS, mapmakers had to decide what the edges of the known world looked like, and this film traces how they did it. It moves from the Roman Empire, which marked the borders of its territory in stone and on parchment, through medieval Europe's travel accounts and portolan charts, to the age of Marco Polo, asking whether he actually had an atlas guiding him toward China or was simply following secondhand reports. Cartographers, historians, and surviving manuscripts anchor the story, showing how each era filled in blank ocean and unknown continents with a mixture of observation, rumor, and outright invention. The film treats the history of mapmaking as also a history of how societies understood their own place in the world, and how much of that understanding was guesswork dressed up as fact. Running at feature length, it gives the subject room to move region by region rather than rushing through it.