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View looking west at stone/brick foundation of the Speakers' Platform—called the rostra. This is the long horizontal wall that runs across the center of the image. The Forum is in front of it, and behind it are the 8 columns of the Temple of Saturn, 3 of the Temple of Vespasian and Titus, and behind that the Tabularium.
Originally the prows of six ships that were defeated by the Romans at the battle of Antium in 338 B.C. were displayed on the front of it. Speakers would stand on the top of the rostra and address the people in the Forum. The top of the rostra was actually littered with all kinds of monuments/memorials.
This structure is called the rostra which refers to the rams of warships that were used to batter their opponents' ships. The singular is rostrum, but because 6 rams were attached to the platform, it was known by the plural form of rostrum—rostra.