Dazar'alor is King Rastakhan's palace in Zuldazar. The Great Seal, in its interior chamber, serves as the Horde's embassy on Zandalar and includes some portals to each major city and expansions, profession trainers, bank and guild banks, transmogifier and a mission table.
In the Battle for Azeroth beta, there was an Unknown Device in Dazar'alor that served as a portal to the Chamber of Heart. It dated back further than the Zandalari knew. It was removed during beta.
^Quest:The Word of Zul: Dockmaster Cobo says: He was wrong. Oh there was damage, but Zul fled, with our fleet, and started a few wars. Those of us who stayed, endured. We rebuilt. Because THAT is what it means to be a Zandalari.