Skyscraper located in downtown Seattle, constructed at roughly the same time Baal arrived on Earth. Baal took charge of the building's design, lacing the entire superstructure with naquadah. He placed a detonator somewhere in the building so that he could use the tower as blackmail to prevent Stargate Command from pursuing him.
Baal's company, Farrow-Marshall, had tapped into secure communications between the S.G.C. and the rest of the United States government. Learning by these means that Stargate Command intended to capture him he chose to prove the truth in his word, initiating a 45-minute countdown before the detonation of the tower.
Civilians were evacuated within a five block radius, but when Samantha Carter discovered that the tower itself was made with naquadah, she realized this was clearly inadequate. The Prometheus used its Asgard transporter to beam the entire structure into space, where the naquadah exploded.
Two hours after the incident Julia Donovan of Inside Access arrived on the scene. Her report revealed the cover story established by the government in that a gas explosion was responsible for the destruction of the building. Though this excuse was lousy at best, conspiracy theorists almost immediately began spinning alternative possibilities. Many pointed out that the amount of rubble at the site was significantly less than a building the size of the Halcyon Tower would have generated.
Ex Deus Machina - Baal tells the S.G.C. that he is aware of their plans to capture him, and informs them that the Halcyon Tower will explode in less than an hour.