The picture above is the arch of Constantine. The picture was taken from the porch of the coliseum. It is always difficult to project the size of a structure from a picture. Sometimes perspective helps. As one sees the relationship between the arch and the people passing by. Only then does one get a sense of the size of the arch.
The two picture below where also views from the coliseum. they are views of part of the Roman Forum. which is where we headed next. Because the Forum is much older, it is more like an archeological site. As Mason stated, one needs to use his or her imagination to picture what the forum might have looked 2500 years ago.