In the Tang Dynasty, the Yellow River Iron Bull was stored in Pujin Ferry Ruins Park on the east bank of the Yellow River in yongji city, Shanxi Province, and was cast in Kaiyuan 12 in the Tang Dynasty. At that time, in order to ensure that the salt produced by the local nitrate pool in Hedong (Yuncheng) could be continuously supplied to Chang 'an, when the iron cable bridge was built at Pujin Ferry, it was cast into an anchor. In fact, there were two schools of iron cows at that time. At present, only one group on the east bank of the river has been excavated, and the other group on the west bank has not yet been discovered.

There are four iron cows, four iron men, two iron mountains, four iron piers and seven iron columns unearthed. Since the excavation of 1989, it has been displayed in the open air without any shielding measures. Visitors can also have close contact during the visit, including touching and taking photos. It is forbidden to touch and photograph cultural relics that look different from the routine to prevent damage. In fact, this method is also a very different kind of cultural relics protection measure taken by experts after textual research.

When the Yellow River Tieniu was first excavated, it was well preserved because it had been under the Yellow River for a long time and was closed by sediment and river water. Because of its huge size (the iron cow is about 3 meters long and weighs 45-70 tons), it did not move after excavation, and the corresponding protection measures did not keep up. After a period of time, it was found that Tieniu was located in the Yellow River beach area, ten meters below the horizon. Due to the influence of groundwater level, it soon rusted beyond recognition. The surface of the four iron cows is peeling off layer by layer, and if it is not treated in time, it will

In order to protect Tieniu, relevant departments and experts demonstrated various schemes, and finally decided to raise Tieniu by12.2m in situ to get rid of the erosion of Tieniu base by groundwater. In addition, according to the painful lesson of the iron lion cultural relics in Cangzhou, Hebei Province, there is no shelter. (Cangzhou Iron Lion is a cultural relic of the Later Zhou Dynasty, weighing more than 30 tons, with extremely high historical value. 1957, the local government specially built a pavilion to shelter from the wind and rain.

However, due to insufficient sunshine, the iron lion rusted quickly, so 1972 demolished the pavilion. 1994 Cracks appeared in the left hind leg of the iron lion, and then the cracking speed accelerated, and the whole body cracked in many places, especially the brittle cracks on the four legs. Cement was used to water the interior to reinforce the iron lion, but the cement further aggravated the corrosion of the iron lion. As a result, the iron lion has existed in name only, leaving only a rotten shell that can only be maintained by external support. It is a typical failure case in the field of cultural relics protection).

At the same time, after simple rust removal, the appearance of the iron ox is not protected, because the ancients actually considered the rust problem when casting and made articles on pouring materials. In addition, visitors can watch and touch at close range, and the grease on their hands can add a protective layer to the iron cow.

Therefore, the seemingly open-air decoration, without protection, is actually the best protection. Now, after a lapse of 1000 years, the four iron cows and iron men are still vivid and intact, which has to be said to be a blessing.

At the same time, we are also looking forward to the early discovery of the iron cattle in Hexi, standing in front of people again, standing opposite the iron cattle in Hedong, and reappearing the glory of the Tang Dynasty.