Book 5 is oriented on the southern and eastern coasts of the Mediterranean. The discussion includes the known portions of the continent of Africa (essentially as far south as the tropics, 1–46), and then continues to Egypt, which is considered a region separate from Africa (47–64). After an account of Egypt that is limited to its more northern portions, the narrative moves through coastal Asia, from western Arabia north into Judaea and Phoenicia, and to Syria, with a digression on the Euphrates River (65–90). Then there is consideration of the coastal territories of Asia Minor, from Syria around as far as the Troad (Troas) and the Thracian Bosporus (91–127). The book concludes with the Aegean islands not previously discussed (those close to the Asian shore), some of the inland territories of western Asia, and the islands in the Propontis (128–151). The end of the book leads directly into the beginning of Book 6, continuing the examination of northern Asia Minor.

Book 3 of the Natural History, the first geographical book, confines itself to southern Europe, from the outlet of the Mediterranean at the west to the mouth of the Danube at the northeast, excluding the Greek peninsula. After a brief introduction about geography and Pliny’s technique (1–2) and comments about Europe as a whole (3–5), the narrative moves through Hispania (6–30), Gaul (31–7), and Italy from the Alps to Sicily (38–138). The Italian portion is nearly two-thirds of the book, which concludes with the regions east of the Adriatic as far as the Danube (139–51). Discussion of mainland Greece is reserved for the following book (NH 4.1–39), whose beginning follows directly on the end of Book 3. The account of the lands west of Italy is limited to the Mediterranean coasts: the remaining portions of the Iberian peninsula and Europe are examined in Book 4 (94–120).

Book 6 discusses the portion of the continent of Asia that had not been examined in Book 5, beginning at the Thracian Bosporus, where Book 5 ended (5.151). Now Pliny continued from the Bosporus around the Asian shore of the Pontus Euxinus, or Black Sea (1–24), with some diversion into the interior of Asia Minor. He then moved into Armenia and the Caucasus (25–35) and the Caspian region (36–49). After a consideration of the extreme north and east of the known world (50–5), the Natural History focused on India, Taprobane, and Ariana (56–106). Returning west, the account moves into the Persian plateau and Mesopotamia (107–141), and then the part of Arabia not previously discussed (142–77), followed by Aethiopia (178–97), and concluding with various islands (198–205). The final portion of the geographical books of the Natural History is about terrestrial parallels (206–20).

C. Plinius Secundus was born at Comum (modern Como) in late ad 23 or sometime the following year. Comum, at the southern end of Lake Larius (modern Lago di Como), had been an obscure Celtic village until a century previously, when the Romans established a presence there. Virtually nothing is known about Pliny’s youth or education, but by ad 47 he had embarked on an equestrian military career in Germania under the command of Cn. Domitius Corbulo. He had returned to Rome by the ad 50s, and seems to have remained relatively obscure during the principate of Nero. But with the accession of Vespasian – whom he already knew – in ad 69 he returned to public service and became a procurator (financial officer), with positions in various locations, including Narbonensis, Tarraconensis, Belgica, Africa, and perhaps elsewhere. He became a close advisor to the emperor, confering with him on a daily basis when in Rome. He also practiced law. Eventually he became fleet commander at Misenum, the Roman naval base established by Augustus at the end of the long peninsula that forms the western side of the Bay of Naples. His sister Plinia and her son, also C.

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.

One of the features of the Natural History is the catalogue of topics and sources that comprises Book 1, a rare component of an ancient text. It provides the subjects of each book, followed by a list of the number of items within it. For Book 2 this is limited to “facts, investigations, and observations,” but for books 3–6 there is the number of “towns and peoples, famous rivers, famous mountains, islands, towns and peoples that have perished,” and then the summary, “facts, investigations, and observations.” The actual numbers for Books 3 and 4 are missing. Only the number of islands (118) survives for Book 5, and Book 6 has the complete sequence of numbers.

Book 2 of the Natural History, the opening book of the text proper, is not strictly geographical, but its discussion of the cosmos is a fitting introduction for the geographical examination that follows. There is an emphasis on the divinity (deus) and its relevance to Roman life, yet this is a divinity that has little or no concern in human affairs. This lays the groundwork for the sense of utility that underlies much of the Natural History, more apparent, perhaps, in practical sections such as those on agriculture and zoology than geography.