Looking at their structure and elevations, archs can be divided into archs with one gate, with three or quadrilateral.
- Archs with one gate.
The single arch with one gate crowned by an entablature with an inscription. It is often based on columns or engaged pillars. Architrave on columns supports a cornice: There a text explaining the cause of its erection can be read. Triumphal archs built on bridges should also be mentioned in this section, though they are described in the page on engineering works -the Bridge of Alcantara BASIC INFORMATIONand Martorell one-.
Elevation of the Arch of Cabanes
In Hispania can be found the:
- Arch with three gates.
Archs with three gates were the most usual in Roman world, but not in Hispania. They kept their habitual structure: two lateral small gates and a wider and higher central one. They were often used as "control gates" to cities: the central one -bigger than the others- were designed for carts and animals; lateral ones for people: one for entering, the other as exit.
Triumphal archs with three gates
The only arch of this kind in Hispania is the famous Roman Arch in Medinaceli:
- Four-sided arch.
As its name shows it has four sides. Its square -or slightly rectangular- plan supports in each side an arch that -it is clear- directly communicates with its opposite and, in a perpendicular way, with the others.
Four-sided arch: Plan and perspective.
It is the rarest of all Roman archs in Hispania. It only remains one: Arch of Capera.
- Commemorative columns
There are few samples of commemorative columns in Hispania, though they were probably more frequent than it could seem. Four columns in the province of Ourense, in San Juan del Rio are the most outstanding. Two of them show the inscriptions devoted to Emperors Flavius Claudius Julianus and Constantinus Augustus.
"Three columns of Ciudad Rodrigo", are also important: they had the function of marking borders between provinces of Mirobriga and Lusitania. They can also be erected to the glory of Emperor August. Their inscription let us read:
Emperor Caesar Augustus, Pontifex Maximus, after holding for twenty-eight times the Power of Tribune, ordered in his thirteenth Consulate as a Pater of the Land that these places were the borders for Mirobriga and he wanted that it be as valid as those of Bletisa.”
Doubtless, the best instance of these works is the famous Traian Column at Rome. It is decorated with a spiral of relieves dealing with scenes of his campaignes in Danube and with inscriptions.