Between the Rioja municipality of Logroo and the Alava municipality of Lanciego in Spain is where you'll find the Roman bridge of Mantible or Assa, which spans the Ebro River.

Its maximum height is 30 metres, and its length is 164 metres. Only one of the two semicircular arches that existed when the study was conducted in 2018 by architect Manuel Fortea of the company Vault Zafra to determine its state of conservation is still standing (on the Alava side), and there are only fragmentary remains of the remaining pillars. What remains of the arch is a testament to the high quality of the stonework employed in its construction.

The bridge was originally thought to have been built in the first half of the 2nd century, smack dab in the middle of the Roman Imperial Period. However, more recent research has relegated the bridge's construction date to the 11th century, labelling it as Romanesque due to its striking similarities to the Puente la Reina bridge in Navarre, which also dates to the 11th century. Both bridges were likely constructed to connect the two most important cities in the kingdom of Nájera-Pampl Its inactivity status and the exact date it was terminated are both mysteries. After being out of commission since at least the middle of the 1600s, it finally succumbed to history.

In 1983, it was designated as a National Monument and thus protected as a Cultural Asset.

After conducting an in-depth analysis of the area around the bridge's ruins, Manuel A. Martn Bueno and José Gabriel Moya Valgaon determined that the bridge had seven semicircular arches, six rectangular pillars with spurs and cutwaters, and two ground-level accesses on either side. In 2018, however, a study led by Manuel Fortea of Vault Zafra concluded that its framework consisted of six semicircular arches.

Because the left bank is lower than the right, the arches on the Mantible Bridge have varying heights and spans to compensate for the uneven terrain. The bridge's deck is also sloped to accommodate the uneven heights of the arches. Each arch had its own pier, except for the first, which was supported by a left-bank abutment with a hole in its top. If the river were at its average level, the water would flow under the second arch; if the river were at its highest level, the water would fill all six eyes.

Two arches once spanned the river, but by the turn of the 21st century, only one stood on each bank. The one in lava, on the left bank, has a clear passage height of 11.90 metres and a span of 20.40 metres. The La Rioja structure on the right has a clear passage height of 10.20 metres and a span of 10.20 metres. The so-called "first" arch and the "second," or central, arch once rested on the same abutment, but the latter has since vanished—likely as a result of deliberate blasting that damaged the abutment (causing a twist of about 6 or 7 degrees and a vertical tear along the axis). Both the damaged abutment and the area around the keystone of the first arch are scheduled to undergo consolidation works in 2019, as well as subsequent monitoring.

After the Ebro's flow increased on January 24, 2021, the arch on the river's right bank, in Rioja, collapsed. The city of Logroo had just begun soliciting bids for consolidation work when the incident occurred.