The Vigo Halo: The challenges of connecting a city vertically

As of a few weeks now, Vigo has a new architectural symbol. It is the Halo, an urban elevator that ascends 50 meters to a large elevated metal walkway overlooking the estuary. The Halo connects two levels of the city, solving a mobility problem while giving a new image to the urban skyline.

Making the Halo a reality posed numerous challenges due to its location, dimensions, and technical specificities. Its construction was carried out at night in order to interfere as little as possible with the life of the city, having been completed on schedule with no workplace accidents.

The social side of the Halo

The two Halo elevator cabins, with a capacity for 17 people each, connect the lower part of the city around García Barbón Avenue with the higher part near Vía Norte, in a trip that takes 30 seconds. For the residents of Vigo, this means reducing a route of several kilometers with a 50-meter drop and avoiding the barrier posed by the AP-9 highway.

In this way, the Halo also improves access to Vialia, a shopping center that houses the train station, located not far from the bus station. Its construction is part of the Vigo Vertical program, an urban development strategy promoted by the city council that seeks, among other objectives, to favor urbanmobility to promote social inclusion and avoid discrimination. In recent years, the city has incorporated elevators and mechanical ramps to facilitate access in areas with a difficult terrain, making life easier for people with reduced mobility.

A new symbol for the city

Along with the social benefits of the Halo, it also has a symbolic importance. The two elevators, installed in the 50-meter-high concrete tower, disembark on a large 4.5-meter-wide ring-shaped walkway, 86 meters in diameter and 190 meters long, which serves as a lookout point to enjoy views of the city and the Vigo estuary.

This walkway is divided into two sections, one covered and another uncovered, which allows visitors to also enjoy it on rainy days. Its shape is reminiscent of artistic works such as Chillida's Praise of the Horizon, creating an artistic connection with that sculpture and giving a new image to the city.

The structure has ornamental lighting consisting of 8,800 LED points that will fill the Halo with color to celebrate different anniversaries and events.

A highly complex construction

As a structure which combines civil engineering and architectural features, the construction of the Halo was complex. It can itself be considered a large sculpture, consisting of a 36-meter tower of reinforced concrete, a 700-tonne metal structure, and a covering of 1,320 square meters of glass and 4,700 square meters of solid surface, a highly moldable covering material made of alumina trihydrate (ATH) and acrylic materials.

The complexity of its construction was increased further due to its location in the middle of the city, next to a school, a shopping mall, an intermodal station, and a highway in constant operation. Traffic was maintained open at all times on the AP-9, which forced us to carry out part of the work at night and to divert traffic with the help of several simultaneous and programed traffic lights during the day.

The tower foundations are direct. To begin construction, various safety measures were taken, including building a screen of micropiles in front of the large vertical reinforced retaining wall for the highway next to the construction site to prevent possible landslides.

The elevator tower, built with 600 cubic meters of reinforced concrete and 250 tons of corrugated steel, was constructed using a climbing system over 34 calendar days. The metal structure, which weighs around 700 tons in total, was then raised. This is where Ferrovial's initiative came into play: to reduce working at height and to ensure the safety of workers, the modules were pre-assembled on the ground and then hoisted, once complete, to the top of the structure. All this contributed to speed up the process and improve the construction system, reducing 34 planned hoisting operations to only nine. This resulted in a reduction of 2.5 months with respect to the initial work program.

The execution of this metal structure forced us to combine daytime and night work for five months. Those parts that had to be executed from the highway or which in some way interfered with highway traffic were carried out during the night. This considerably increased the complexity of the project.

Today, this large structure is supported by the reinforced concrete tower and two other metal supports, but during its construction it was necessary to place 7 temporary props for the assembly of the structure.

Once the structure was finished, it was time to coat and embellish it. In total, the Halo has 1,320 square meters of screen-printed curved glass, with a gradient that plays with light and brightness, and 4,700 square meters of solid surface, which gives it its characteristic white color.

Collaboration and teamwork

Even before the construction became a reality, the Vigo architect Alexandre Mouriño, author of the design, in collaboration with the prestigious engineering firm Arenas y Asociados and the Portuguese architectural firm NOARQ, won the international Loop Design Awards in the unbuilt architecture category.

Collaboration has been essential in melding the architectural, structural, and technological aspects of this project. We have relied on a multidisciplinary team and on the contribution of our in-house expertise for its execution. Thanks to the work of more than 500 workers, Vigo now has a unique architectural attraction and a new symbol for the city.

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