The tower was completed in 1998 as the centerpiece of Expo '98, a World's Fair themed around "The Oceans, a Heritage for the Future." The choice of theme was deliberate: 1998 marked the 500th anniversary of Vasco da Gama's voyage to India, the maritime achievement that launched the Portuguese Empire. At the tower's base, a three-story building served as the European Union Pavilion during the fair. When the Expo closed, plans to convert the base into commercial office space failed to attract tenants. The building sat largely empty, hosting occasional one-off events, including the world premiere of the redesigned Mini car in 2001. Both the observation deck and the restaurant closed in October 2004, and for several years the tower stood as a monument to the familiar post-exposition problem: what to do with the fair when the fair is over.

The architects, Leonor Janeiro, Nick Jacobs, and the firm Skidmore, Owings and Merrill, drew their design from Portugal's nautical heritage. The tower's vertical mast rises from a base that enters the river like the bow of a ship, supported by pillars that form a terrace above the water. A metallic tubular structure curves away from the mast like a sail filling with wind, and at 120 meters, a platform forms the crow's nest, housing what was originally a revolving restaurant and viewing area. The engineering firm Martifer assembled the structure, which manages to be both monumental and graceful, its lattice framework allowing the Tagus winds to pass through rather than push against it.

The solution to the tower's post-Expo emptiness arrived in stages. Portuguese architect Nuno Leonidas designed a 20-floor, 178-room luxury hotel to replace the original base building. Demolition began in July 2007, and the five-star Myriad hotel opened in 2012, wrapping around the base of the tower in a sleek, contemporary form that contrasts with the lattice structure above. Then, in 2018, Michelin-starred chef Martin Berasategui opened the panoramic restaurant Fifty Seconds in the space that had been the observation deck. The name refers to the elevator ride to the top. Within a year, the restaurant earned its own Michelin star, transforming a closed-off platform into one of Lisbon's most coveted dining experiences, with the Tagus River, the Vasco da Gama Bridge, and the city spread out below.