Dārat Juljul is a named locality. Although dārah can refer to a circular or enclosed tract of land, the full expression functions here as a proper place name, not as two common nouns to be translated independently.
The ode has already named Siqṭ al-Liwā and Maʾsal. Another location now becomes the name of a particularly memorable day. Geography organizes recollection: each place brings an emotion or event into view.
The next verse begins wa-yawma ʿaqartu, linking its action closely to the day just singled out and turning memories into a connected narrative.