Figure 1. A Roman army in full marching order, complete with its siege weapons, crossing the bridge over the Spanish river Tagus at Alcantara.
The Romans could never have built such broad straight roads without crossing rivers, but Roman engineers were experts in the art of bridge-building. In some cases pontoon bridges made of boats covered with planks were built, but many permanent stone bridges were also constructed, traces of which still remain.
The bridge at Alcantara
In Rome itself, many old bridges across the Tiber are still standing, and in Britain traces of bridges at London and Newcastle can be seen. But by far the most impressive Roman bridge standing today is that at Alcantara in Spain (see Fig 1). The bridge has, in fact, given the town its name, as Alcantara in Arabic means 'The Bridge'. This bridge was built between AD 105 and 116 by the combined efforts of many neighboring peoples. The name of the architect, and pride in this achievement, have been preserved in an inscription found in a small chapel not far from the bridge: 'The noble Caius Lucius Lacer built this bridge with miraculous skill, destined to last as long as the world itself.' The bridge is 617 feet long, and passes a height of 100 feet above the river Tagus, which it spans. The bridge is built entirely from blocks of granite, some weighing as much as six tons, and no cement was used. The architect calculated the stresses so accurately, and the blocks are so carefully any shaped, that they have stayed in position for over 1,800 years. The road is wide enough for eight men to cross the bridge abreast, and it can hold 2,000 people at a time.
One of the main features of the bridge is the arch which stands in the middle. Although it is primarily intended as decoration for the bridge, it also served a useful military purpose. A handful of soldiers stationed at the arch could hold the bridge against a very large enemy force. By any standards the bridge at Alcantara deserves to be considered one of the world's greatest architectural achievements.
Other famous Roman bridges
|One of the oldest Roman bridges still standing, the Pons Fabricius, which was built across the Tiber at Rome in 62 BC.
|The magnificent bridge built across the Danube by the Emperor Trojan. It is more than 1,200 yards long and some of its pillars are still standing
|A Roman bridge which still stands in one of the most isolated parts of the world – in Algeria, on the edge of the Sahara