Which river does the Roman stone bridge of Alcantara cross?

Crossing the Tagus River at Alcántara in Spain, the Alcántara Bridge is a masterpiece of ancient Roman bridge building. The bridge was built between 104 and 106 by an order of the Roman Emperor Trajan in 98 AD, who is honored by a triumphal arch in the center of the bridge and a small temple at one end. The Alcántara Bridge has taken more damage from war than from the elements. The Moors destroyed the smallest arch on one side while the second arch on the other side was destroyed by the Spanish to stop the Portuguese.

The original length of this bridge was 190 metres (620 ft). It is now 181.7 metres (596 ft) long The clear spans of the six arches from the right to the left riverside are 13.6 metres (45 ft), 23.4 metres (77 ft), 28.8 metres (94 ft), 27.4 metres (90 ft), 21.9 metres (72 ft) and 13.8 metres (45 ft).