In P’sukei D’zimra, Tehillim 147verse 12 says : שַׁבְּחִ֣י יְ֭רוּשָׁלַ͏ִם אֶת־ה’ הַֽלְלִ֖י אֱלֹקַיִךְ צִיּֽוֹ. Yerushalayim, praise Hashem, praise your Elokayich, Tzion.
The next Pasuk say:
For He made the bars of gates strong. כִּֽי־חִ֭זַּק בְּרִיחֵ֣י שְׁעָרָ֑יִךְ
Radak explains the idea of , “He made strong”, כִּֽי־חִ֭זַּק .
One should never fear that an enemy is coming upon you, because Hashem, The Source of all powers, will guard you as if you had strong bars on your gates.
This idea connected me to the story of Gan Eden and the gates have extra enforcements with the flaming swords of the angel protecting the garden in Eden. וַיַּשְׁכֵּן֩ מִקֶּ֨דֶם לְגַן־עֵ֜דֶן אֶת־הַכְּרֻבִ֗ים וְאֵ֨ת לַ֤הַט הַחֶ֙רֶב֙ הַמִּתְהַפֶּ֔כֶת לִשְׁמֹ֕ר אֶת־דֶּ֖רֶךְ עֵ֥ץ הַֽחַיִּֽים and east of the garden of Eden were stationed the cherubim and the fiery ever-turning sword, to guard the way to the tree of life.
Perhaps Yerushalayim represents our unique garden containing all our moments of tzikdus, our Mitzvos, our good deeds, and particularly the moments of Teshuva, the moments we have chosen a Derech to attach to Hashem, aka ־דֶּ֖רֶךְ עֵ֥ץ הַֽחַיִּֽים. This is something Hashem protects so it is not damaged by a human being and accessible. Perhaps the idea is that even if an enemy is threatening us, we call turn on the security of ־דֶּ֖רֶךְ עֵ֥ץ הַֽחַיִּֽים to address any threat biezras Hashem.