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Moss-Covered Basalt Structure Embracing Geothermal Caves

Authors:
Michael Godden, Raphael Costes, Nina Fradet
Moss-Covered Basalt Structure Embracing Geothermal Caves
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Constructed from local basalt, the structure's form embraces the natural landscape and integrates a central void that provides access to the geothermal caves while accommodating a café for visitor engagement.
5 key facts about this project
01
Constructed primarily from locally sourced basalt, emphasizing sustainability.
02
The design features a central void that enhances natural light and access to the caves.
03
Moss growth is integrated into the structure for a natural aging effect.
04
Intersecting staircases provide multiple levels of observation and engagement.
05
A café within the structure operates independently while connecting visitors to the site.

The Basalt Tower is located in Iceland, close to the Grjótagjá caves, which are known for their geothermal pools and unique geological features. The design aims to enhance the visitor experience while respecting the natural landscape. At the heart of the design is a central void, which creates interaction between the architecture and the environment. This approach encourages visitors to engage more deeply with the unique characteristics of the site.

Architectural Concept

The design of the Basalt Tower reaches out to the landscape where it sits. The visitor experience begins with a ramp that leads down into the earth, guiding people toward the caves in a deliberate way. This descent helps visitors feel connected to the geological features of the area. It allows a gradual transition into the site, preparing them for the beauty they will encounter as they approach the cave entrance.



Spatial Organization

The tower’s structure consists of two concave walls that frame the space while allowing visibility through the design. Inside, intersecting staircases make it easy for people to move around. These staircases create different levels of observation that enhance the experience of the surrounding landscape. Near the main void, which offers access to the rock formations, a café and technical spaces are included. This arrangement allows these facilities to serve visitors efficiently without disrupting the flow of traffic.



Materiality and Integration

Basalt rock has been selected as the primary material for construction, sourced locally to strengthen the connection to the site. By using this material, the tower not only remains sturdy but also allows for gradual change over time. The basalt can support moss growth, helping the structure blend in with its surroundings. This aspect of the design aims to honor the natural environment by allowing the tower to coexist with local geology.



Visitor Engagement

The design encourages exploration through carefully planned pathways, providing various routes to the observation points and the café. This thoughtful layout helps visitors navigate their surroundings more easily. It creates spaces for social interaction and areas for quiet reflection. One notable detail is the structure’s formwork, which includes pockets designed for moss to grow. This design choice demonstrates a commitment to harmonizing human activity with nature, allowing the architecture to change and adapt over time within its environment.

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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.

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