Book 4, the shortest of the geographical books of the Natural History, begins at the Acroceraunian Promontory on the west coast of the Balkan Peninsula, at the northern edge of Epiros. It thus connects with NH 3.145, where Pliny completed his discussion of the Adriatic coast. The book includes the entire Greek peninsula, described in a counter-clockwise fashion from Epiros through the Peloponnesus and north to Macedonia (4.1–39), Thrace and the Aegean (4.40–51), the Greek islands (4.52–74), and the European side of the Black Sea (4.75–93). Rather than cross into Asia at this point, and continue along the eastern coast of the sea, the narrative heads back west into northern Europe (3.94–101), and then passes through the British Isles into the interior parts of Gallia and Hispania (4.102–120), regions that were not discussed in Book 3. The circular itinerary, unusual in Greco-Roman geographical studies, allowed Pliny to complete Europe before moving to the other continents, yet retain the coastal orientation that is an essential part of the geographical portions of the Natural History. But it meant that the central nature of Europe – the location of Rome – was emphasized before moving to the other continents.