There's no mistaking the Rainier Tower. It rises from an 11-story pedestal, leaving the streets open and pedestrian-oriented. Despite its 40 stories and 538,000 square feet, the Tower occupies only 25 percent of the block bounded by 4th and 5th avenues and Union and University streets. The remainder is devoted to Rainier Square's three-level retail atrium and landscaped plazas, where Rainier Square and the Tower are integrated.

The building was the third success for design architect Minoru Yamasaki and project architects The NBBJ Group (formerly Naramore, Bain, Brady & Johanson). The firms had previously collaborated on the IBM Building in downtown Seattle and on the Federal Science Pavilion for the 1962 Seattle World's Fair before teaming to design the Rainier Tower.

The Tower's grace belies its strength and utility. Its design underwent three environmental tests before construction. It was tested first for strength in the event of a severe earthquake, then for stability during high winds. The results proved Rainier Tower as one of Seattle's safest buildings. Even its unusual shape was tested, finding that it would eliminate the "canyon effect" of strong winds that can occur around modern high-rise buildings.