The Via Sacra (or Sacra Via) in Rome is the road that connects the valley that is now dominated by the Colosseum, passing over the crest of the Velia, to the Forum Romanum. People celebrating a triumph used this road. What you can see today when you walk from the Temple of Caesar to the Arch of Titus is the road as it was in the age of Augustus.
However, it is possible to imagine what it looked like at a later stage. In an article originally posted in the American Journal of Archaeology (in 1923), Esther Boise Van Deman showed how the area was restructured during the last regnal years of Nero: a straight road leading to the Vestibulum of the Golden House (where the Colossus stood) with basilicas to the left and right – now the site of the Basilica of Maxentius and the Horrea of Vespasian. The article has been made available now by LacusCurtius‘ Bill Thayer, and you can find it here.