Bible verses about Fortresses
(From Torrey's Topical Textbook)

Places strong by nature Numbers 24:21 Places fortified by art Jeremiah 51:53 The security of a nation Isaiah 33:16; Daniel 11:10 PLACES USED AS Cities Judges 9:31; Nehemiah 4:2 Strong-holds Judges 6:2; II Chronicles 11:11 Forts II Samuel 5:9; Isaiah 25:12 Strong towers II Chronicles 26:9 Afforded protection in danger Judges 6:2 Defended against enemies Nahum 2:1 OFTEN Entered by the enemy Daniel 11:7 Spoiled Hosea 10:14 Levelled Isaiah 25:12 Deserted, &c Isaiah 34:13 Destruction of, threatened Isaiah 17:3 ILLUSTRATIVE OF God's protection Psalms 18:2; Jeremiah 16:19 Christ, the defence of saints Isaiah 33:16 Protection afforded to ministers Jeremiah 6:27