The older (Hallstatt period, 800-450 BC) and younger Iron Age (La Tène period, 450 BC - around the birth of Christ) are associated with the term Celts in our latitudes. The Celtic heartland covered an area from eastern France to Austria and from Switzerland to the southern half of Germany. The iron processing that gave the area its name first appeared in Europe at the turn of the Urnfield and Hallstatt periods. As the most valuable metal, iron was initially used purely as an ornamental metal as an inlay in bronze objects. Tools and weapons were increasingly made of iron, while jewelry and metal tableware continued to be made of bronze. The extraction and processing of the new metal is a new technology in that iron does not occur in its natural state like copper and bronze (natural copper alloys), but has to be melted at high temperatures from ore of a completely different character (limonite or hematite in our case). In the Iron Age, vessels were produced for the first time with the help of the potter's wheel; before that, pottery was formed "freehand".

Knowledge of the Iron Age in Hesse has recently been expanded by the excavations on the Glauberg and in the Bad Nauheim salt works. The finds of the century from the princely burial mounds on the Glauberg show a level of cultural development in the Iron Age that had not been expected for our region, as it was previously considered to be on the edge of the Celtic heartland. The finds provide evidence of links to the Mediterranean region. We know very little about the settlements in the lowlands. The few known Celtic houses in our area are small (4x6 m) and appear poor. Our knowledge has been handed down by the Romans from a final phase of Celtic culture; the Celtic gods appear to us in Roman garb. The viewer's prior knowledge will always play a role in the interpretation of pictorial representations. Very cautiously, we can say that a rather high form of polytheism prevailed. The burning of the dead is generally interpreted as a belief in a spiritual/soul existence, as burning frees the soul from the body. The high veneration of the head, which manifests itself in many representations of heads on stelae, vessels and buildings, goes in a similar direction. Temples are only known from a time when they can be clearly attributed to Roman influence. The Celts disappear around the birth of Christ. How, where and why we do not know. The Romans emerge as a new power and begin to conquer the area north of the Alps. Although this does not de facto end the Iron Age, archaeologists and historians divide and name the following epochs according to different criteria.

The burial mounds in the Wiesbaden area mentioned in the Stone Age and Bronze Age chapters also contain burials from the Iron Age. The three smaller groups of mounds in the "Ruhehaag", in the "Kohlheck" and at the Fasanerie seem to belong mainly to the Hallstatt period. A single mound near the pheasantry with a richly furnished grave was certainly erected in the early La Tène period. Iron Age hilltop settlements, whose fortification walls, which have crumbled into ramparts, are impressive monuments in the surrounding area of Wiesbaden. In the city area, including the districts, only the fortification on the Kellerskopf in Naurod can be dated to the Iron Age. Some of the other "ring walls" mentioned in the literature no longer exist, such as the rampart on the Würzberg described by Carl August von Cohausen, which was only one foot high at the time; for others, it is even disputed whether they were ever real fortifications, regardless of the period.