Baltia, Basilia or Abalus is a mythic island in northern Europe mentioned in Greco-Roman geography in the connection of amber.
It presumably corresponds to a territory near either the Baltic Sea or the North Sea, perhaps the coast of Prussia, the island of Gotland, Sweden, or of the Jutland Peninsula.
Pliny the Elder (HN. 4.95; 37.35-36)
Diodorus Siculus (v. 23):