Smith's Dictionary
the fifth of the six cities of Judah which lay in the “wilderness.” (Joshua 15:62) Mr. Robinson expresses his belief that it lay somewhere near the plain at the south end of the Salt Sea.
International Standard Bible Encyclopedia
(`ir ha-melach; Codex Alexandrinus hai pol(e)is halon): One of the six cities in the wilderness of Judah mentioned between Nibshan and Engedi (Jos 15:62). The site is very uncertain. The large and important Tell el-Milch (i.e. "the salt hill"), on the route from Hebron to Akaba, is possible.