Psalm 48

The psalm ends with a guided walk: "Walk about Zion, and go round about her: tell the towers thereof. Mark ye well her bulwarks, consider her palaces; that ye may tell it to the generation following." That is a defense inspection turned into a teaching tour. Counting towers and checking the ramparts was ordinary municipal work after an attack, and the psalm tells fathers to take their children on it.

Jerusalem's strength was its shape. The old city sat on a ridge with deep valleys on two sides, so an attacker had one practical approach. "Beautiful for situation" is a comment on terrain before it is a compliment.

"The kings were assembled, they passed by together. They saw it, and so they marvelled; they were troubled, and hasted away." A coalition army arriving, taking one look, and leaving is a recognizable ancient event — sieges were expensive and armies fed themselves off the countryside, so a hard target could be abandoned.

"Thou breakest the ships of Tarshish with an east wind." Ships of Tarshish were the largest deep-water merchant vessels known to that world, named for a distant western port. The east wind is the sirocco off the desert, a hot, violent wind that could wreck shipping. Israel was not a sea power; the image is of God sinking the biggest thing on the water.