Arch of Septimius Severus
Septimius Severus was a Roman emperor about 200 AD who decided to put up a stone triumphal arch in the Roman forum in order to remind people about his military victories over the Parthians east of Rome. In this picture, you can see the Roman Senate House in the background on the left.
This is the arch from the other side. You can see that this arch, built more than a hundred years after the Arch of Titus, has a very different artistic style. Instead of big relief carvings on the inside of the arch, this one has several small relief carvings on the front and back.
For more about the Arch of Septimius Severus, please check out these books from Amazon.com or from your library:
The Colosseum & the Roman Forum, by Martyn Whittock (2002). For kids.
The Roman Forum, by Michael Grant (1970). Out of date, but Michael Grant is an entertaining writer with a simple style which teenagers may appreciate.
Ancient Roman Art, by Susie Hodge (1998). For kids.
Roman Art: Romulus to Constantine, by Nancy and Andrew Ramage (4th Edition 2004). The standard textbook.
The Arch of Septimius Severus in the Roman Forum, by R. Brilliant (1987). Unfortunately out of print, but libraries should still be able to get it.