The Beaker culture arrived around 2,500 BC, introducing drinking and food vessels constructed from clay, as well as vessels used as reduction pots to smelt copper ores. It was during this time that major Neolithic monuments such as Stonehenge and Avebury were constructed. By heating together tin and copper, which were in abundance in the area, the Beaker culture people made bronze, and later iron from iron ores. The development of iron smelting allowed the construction of better ploughs, advancing agriculture (for instance, with Celtic fields), as well as the production of more effective weapons.