Celtic art is notorious for its spirals and complex symmetry, along with surreal and abstract imagery. Given that their religion frowned upon written literature, they did not leave behind any descriptions of their art. All that we “know” about the meanings of various symbols and styles is extrapolated from the remnants of their legends, mythos, and environment. The style of Celtic art we typically imagine is from the La Tène era starting in 500 BC and was heavily influenced by the Greco-Romans. Unlike the Greco-Romans, the Celts preferred to abstractify the mundane. Similarly to them, they put art on everything.
Art was found everywhere: on weapons, jewelry, clothing, sculptures, buildings, and the landscape. Designs decorated even the most mundane objects, such as tools. Often, the designs are just of complicated spirals and complex symmetrical patterns. However, there are plenty of designs showing people, warriors, animals, and deities. One of the most well-known piece of ancient Celtic art is the Gundestrup Cauldron.
The Gundestrup Cauldron was found in disassembled in Gundestrup in the Jutland peninsula of Denmark. Made up of 12 rectangular plates (5 long, 7 short), a circular base plate, and two pieces of tubing, this masterpiece has images adorning its exterior and interior. Each plate is 97% silver with some gilded patterns, while the eyes of larger figures were inset with glass. Some images shown include plants, humans, bulls, hounds, lions, winged horses, birds, dolphins, and gods.
Shown in the center of this plate, Cernunnos is the Celtic god of fertility and nature. He is usually seen with sexual imagery to reflect his association with fertility (note the snake in one hand and the torc in the other). This is one image of many on the cauldron showing not only animals and gods, but also showing their interaction. This expresses the thin veil between the spiritual and temporal realms, which is prevalent in Celtic religion and art.
On another panel, there is a giant immersing an apparently dead person into a large vessel. There have been two interpretations of this: cauldrons were seen as having magical properties in Celtic culture. It may have been believed that cauldrons could be used for purposes of resurrecting the dead, and that this giant is trying to resurrect the person. Another theory is that it represents human sacrifice to Teutates, the god of war. If the Celts did perform human sacrifice (it is unsure as to whether or not they did), sacrifices to Teutates would have been done by drowning the sacrifice. Although it is unsure whether or not they performed human sacrifice, animal sacrifice was in fact common. For example, two plates show bulls being sacrificed.
For more in depth information on the Gundestrup Cauldron, visit this website.