In the past, this bridge was also known as Qaltoq Gate Bridge due to its proximity to the southern gate of the city. The construction date of the Sardar bridge is on the inner body of the largest arch and inside the beautiful porcelain brick frame, which includes the holy mention of Ya Ali. It has been engraved.
The length of the bridge is about 79.5 meters, its height at the highest point from the river bed is about 12 meters, and its width is about 4.6 meters. The bridge has three spans with gable arches, the middle span being larger than the other spans. There are also two openings with decorative arches on the foundations of the bridge. The foundations of the bridge are 6 meters wide and made of cut stones and are about 2 meters high from the river bottom.

The bases are waterproof in both directions. The aqueducts on the upstream side are polygonal and the aqueducts on the downstream side are semicircular. The main and large opening of the bridge is 11.60 meters wide and about 8.5 meters high from the water level. The smaller openings are 5.50 meters wide and 5.10 meters high from the water level.
In this bridge, in order to lighten the building, reduce the extra load and save construction materials, in addition to creating two decorative arches (which are increased in the form of a step upwards in their range until they reach a round arch in a corner frame ), have created many hollow spaces around the bridge arch and core. The noteworthy point in the building of this bridge is the two vaulted spaces that are created in the foundations resting on the river banks - like the smaller spans of the bridge.

Today, these openings are covered from both sides, and it is not exactly clear whether they were created to make the foundations of the bridge lighter or they were openings that were later blocked to increase the strength of the foundations. In the arches and the body of the building, bricks measuring 5x25x25 cm are used. The surface of the bridge crossing has a relatively steep slope from the middle to both sides due to the high height of the middle opening.
According to the remains, it seems that the river bed at the place of the bridge was paved, which prevented the river flow from washing away the foundation of the bridge and the river bed under the foundations.

Another noteworthy point of Sardar Bridge is the tile and brick decorations on its eastern facade, which is rarely seen in other bridges. On the eastern side of the bridge, there is tile decoration on the top of the vestibules and strips of tiles around the bridge openings, the central opening strip is a 25 cm strip of glazed tiles and bricks, and the side openings strip is a 5 cm row. A meter of blue tiles. On the south side of the central opening, in a rectangular frame, there is an inscription of raised brick, on both sides of which, the date ((1333)) and the word ((Yaali)) are written in Kufic script.
Sources: Bulletin 1356, No. 26, p. 12
Documents and documents of the General Department of Cultural Heritage of Zanjan Province
This bridge is one of the valuable works of the late Qajar period. This work has been registered as number 1485 in the list of national works.