1 Undershaft is located at the heart of the 'Eastern Cluster' of the City of London at the junction of St Mary Axe and Leadenhall Street. When constructed it will be the tallest building in the City of London. The 73-storey tower will be 289.94m tall at a height of 304.94 m AOD. The building acknowledges the importance of culture and public realm for the people who live, visit or work in the City. As well as providing a new public space at street level, it will offer a generous space at the top of the building for a free public viewing gallery, education centre, exhibition space and London’s highest public restaurant. At 281.5 m above ground, the public viewing gallery will be the highest in the City of London and the only one in the City to offer a full, unobstructed view of the capital. Alongside the public viewing gallery will be an education centre with two classrooms for school parties to learn about the rich history of London.

The building targets very high environmental standards in terms of build and operation and is designed to achieve a BREEAM Excellent rating. Horizontal brise soleil, made in white vitreous enamel protect the glazed facade and provide physical shading to the building. The existing basement construction will be reused where possible and an off-site logistic centre will consolidate and minimise vehicle movement during construction.

The external bracing system allows its core to be moved to one side. This provides completely uninterrupted floor plates giving tenants maximum flexibility and efficiency when compared to conventional central cored buildings. The four sky lobbies offer the opportunity to be used as shared spaces for various functions. Careful consideration has been given to the quality of the spaces, air, and daylight, ensuring the building is adaptable to future uses.

The tower is uni-directional, meaning that its subtlety tapered sides will look the same from each angle across the City. This adds to the simplicity of the design and the prominence of the central location in the City of London. By elevating the office reception to the first floor ten meter above ground, a generous, accessible and unique new public space beneath the building will be created, providing much needed relief for pedestrians and cyclists in a dense area of the City.