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Elevated Living Above Active Railways with Mixed-Use Spaces

Authors:
Walter Hjaltested, Caterina Decker
Elevated Living Above Active Railways with Mixed-Use Spaces
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Located above active railway viaducts, the design transforms underutilized infrastructure into a dynamic mixed-use environment with diverse housing options and integrated community spaces.
5 key facts about this project
01
Located above active railway tracks, enhancing urban use of infrastructure.
02
Design includes circular public squares encouraging social interaction.
03
Mixed-use floors accommodate both residential and community facilities.
04
Potential for over 250,000 new homes without requiring additional land.
05
Varied apartment typologies cater to a wide demographic range.

The City in the Sky project makes use of the Greenwich Railway Tracks in London, addressing the city's high demand for housing while enhancing community connections. The design combines residential and commercial spaces in a multi-level urban structure that seeks to foster interaction and accessibility among residents.

Design Concept

The architectural layout reimagines the railway viaducts, which have primarily functioned as storage and maintenance areas, turning them into a lively mixed-use environment. Comprised of a two-story, low-rise structure, the project spans about 5 kilometers, creating a continuous living area that features streets elevated above the ground. This approach aims to connect individual living and working needs with broader community experiences.

Programmatic Elements

Mixed-use floors within the City in the Sky include both living units and community facilities such as kindergartens and workspace offices. This design provides vital services for residents and serves as a sound-insulating buffer between the apartments and active train operations below. By integrating various activities within the same space, the environment promotes a vibrant atmosphere where daily life and work can coexist.

Community Interaction

Pedestrian paths and public squares are woven throughout the design, facilitating movement and fostering social connections among residents. Circular public spaces feature restaurants and cafes, encouraging community engagement and enhancing urban life. These areas contribute to a livelier atmosphere, breaking down the usual barriers often found in city designs.

Housing Capacity

The plan can accommodate over 250,000 new homes without needing to acquire additional land, presenting a sustainable approach to urban development. By offering diverse apartment types, from affordable units to more premium residences, the project meets the varying needs of a dense population. This inclusivity is essential in addressing the ongoing housing crisis in the city.

The City in the Sky concludes with communal spaces that encourage exploration and connection, framed by an inviting streetscape that serves as a gathering point for residents.

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The Buildner’s Unbuilt Award 2025: Celebrating Architectural Creativity and Visionary Unbuilt Designs with a Total Prize Fund of €100,000

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Competition organisers

The Buildner’s Unbuilt Award 2025 is an international architecture competition dedicated to recognizing and celebrating the value of unrealized architectural designs. It invites architects, designers, and students worldwide to submit visionary projects that have not yet been constructed, highlighting the power of ideas and the creativity behind the design process. By focusing on unbuilt work, the competition aims to bring forward concepts that shape the future of architecture and push the boundaries of the profession. 

Participants can compete in three categories based on project scale: Small Wonders (up to 100 m²), Medium Marvels (101–999 m²), and Large Visions (over 1,000 m²). Each category winner will receive €20,000, and additional prizes include honorable mentions, student awards, and a special Best Presentation Award. Winning projects will gain significant international exposure through Buildner’s publicity campaign and a feature article on ArchDaily, providing a unique opportunity to showcase creative ideas to a global audience. 

The Buildner’s Unbuilt Award 2025 encourages entrants to submit any type of unbuilt project, from conceptual visions to detailed designs, celebrating bold innovation without the constraints of realization. Important deadlines: registration closes on October 30, 2025; submissions are due by November 20, 2025; winners will be announced on December 17, 2025.

Buildner's Unbuilt Award 2025

Celebrating your unbuilt architecture visions with a €100,000 prize

100,000€ Prize / 2025 ideas COMPETITION
Prize 100,000 €
Eligibility Open to all
Final registration deadline 30 October 2025

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