Undoubtedly the most publicized inscription is the remarkable letters cut into stone at the base of the Trajan column in about the year 113 BC. These letters are actually typical of all inscriptions of that time. Like Rome these letters were not built in a day, but represented at least 7 centuries of development, from the Etruscan (where the Romans got the alphabet) to the Roman Empire. The letters are perfect in function, conveying a sense of power perfectly. They evolved with the architecture of the time, the connection between these rounded letters and the arched vaults and cupolas of their buildings are obvious.
You may have heard that the ancient Romans could not read or write. Actually, the ancient Romans wrote quite a bit. Much of their pottery was signed. Very often, the bricks used to make buildings were stamped with their makers names. Lead pipes leading to these buildings, by law, were stamped. Scholars have found 200,000 Latin inscriptions and, incredibly, several thousands are still being found every year. Scholarly estimates are at around 30% of all adult men in Imperial times had the ability to read and write.