The Bridge of Mantible (Puente Romano de Mantible) is a ruined bridge located near Logroño. According to some historians, construction of the bridge began in the first half of the 2nd century, well into Rome's imperial period. Others suggest that the bridge was built in the 11th century, near the same time in which the Puente La Reina was constructed over the River Arga, and that both were made to join the two most important cities of the Kingdom of Navarre, Nájera and Pamplona.
Neither theory makes clear at what point the bridge became no longer passable, but there are documents that suggest that it had already fully deteriorated by halfway through the 16th century.
The bridge is 164 meters long, 5 meters wide and reaches a maximum height of 30 meters. It was built with seven semicircular arches, only two of which stand relatively intact today. There are only a few remains of the other five arches. The two standing arches serve as an example of the excellent quarry stone used in the bridge.
References:The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.