An ice box was roughly the shape of a coffin and was constructed from a material with about the same thickness and strength as hardened clay. One weighed about 300 pounds (140 kilograms). During the height of the Netherese Empire, they typically sold for 225 gold pieces.
As a quasimagical item, an ice box only functioned if within one mile (one and a half kilometers) of a mythallar. If within a mythallar's range of effect, an ice box maintained a magical conduit to the Paraelemental Plane of Ice, which provided a constant source of cold to keep food frozen.