It can be difficult to visualize what ancient sites used to look like as you walk among the ruins. This recreation of the Roman Forum set above a photo of the area today gives a good comparative sense.. On the hill to the upper left is the Temple of Jupiter (now completely gone) on the Capitoline Hill, the place to which the Senatorial conspirators fled after assassinating Julius Caesar in 44 BC. To its right and lower down on the hill is the Tabularium, where the archives of Rome were stored (the lower stories remain today). To the right along the roadstead is the Arch of Septimius Severus erected early in the third century AD and which still stands today.
Apart from the total or partial disappearance of many of the structures the biggest change is that the still-standing buildings and monuments had their marble cladding removed for use in other construction projects over the thousand years after the fall of the empire.
From Facebook's Roman History Group.