The Old Forum is the heart of the ancient city — the civic square where the original Roman colonists gathered, conducted business, and participated in public life. It is substantially intact: the paving stones are in place, the Temple of the Septimian family at the northern end still has its columns standing, and the layout of the surrounding buildings is legible.
Walking through the forum, you pass the curia (senate house), the basilica (law court, not a church), and various honorific columns. The Temple of the Septimian family is an imposing structure dedicated to the imperial dynasty in the early third century. The columns of the temple, still standing against the mountain backdrop, make one of the most photogenic scenes on the site.
The forum connects via the main cardo (north-south street) to the theatre to the north and the Arch of Caracalla to the south. Walk this spine of the city from end to end for the best sense of Roman urbanism in North Africa.