Epistula

You see a letter from Cicero to his friend Atticus (dated September 30, 54 BCE), in which he talks about Caesar's plans to transform the Campus Martius. Among the projected buildings, Cicero mentions the Saepta Julia:

"We expect to build, dear Atticus, a building of marble, covered by a roof, in the space where the comitia tributa have been traditionally meeting. The building will also be surrounded by a lofty portico, one mile long, and it will be connected to the Villa Publica"(Cic. Att 4.16.14).