The Arch of Septimius Severus bestrides the most important road in Rome, the Via Sacra, which runs across the Roman Forum. The most significant sacred and political ceremonies of the ancient city took place here and the most evocative of these was certainly the Triumphal Procession. The Lapis Niger, a large piece of black marble, marks an underground space which was probably a holy area dedicated to Romulus. The material is different from the stone found in the rest of the forum.After the Arch and Lapis Niger, you come to the political area of the Forum, the assembly area. This space was used in the archaic era for political and judicial assemblies but it was drastically reduced in size to make room for the forum built by Julius Caesar. Just beyond is the Curia building. Caesar destroyed the original in order to create his forum and built the Curia Julia instead. This in turn was reconstructed in the 3rd century AD by the Emperor Diocletian and is the building you can see today.