This monumental arch is the last vestige of a tetrapylon built to celebrate Emperor Galerius's victory over the Persians (299). Known today as Kamara, the building originally had two parallel triple arches, 37m long and joined by a cupola. The main arch gave onto the Rotunda, and the lateral openings onto the street. All that remains is a part of the western arch with three pillars. The low reliefs narrated Galerius's exploits.