Please see “ A Grammar of the Arabic Language,” by W. Wright, 3rd Ed., Vol II, pp. 198-234. The section “The Status Constructus and the Genitives,” is relevant to the topic and I am quoting below almost verbatim from Article 95(c), page 232:
“(c) To the names of towns, rivers, mountains, etc., when preceded by the words for town, river, etc.; as Madinatu Baghdad “the city of Baghdad; Nahru Alfarat “the river Euphrates’; …; Toure Sineen “mount Sinai” ; Shahru Ramadan “the month of Ramadan.”
I guess the above coming from a well-respected source should be good enough to conclude the matter.