East Cornworthy Reservoir is an existing underground concrete water reservoir, submerged in the Devon countryside. This project will convert the existing building into a contemporary family home with strong links to its surroundings. The new dwelling will break through the rear of the underground reservoir and reaches out into the surrounding countryside. The large, south-facing, glazed walls to the rear maximise the amount of sunlight entering the building whilst focusing your attention on the rural views surrounding the site; creating a strong connection between the internal and external spaces. A sunken courtyard to the front of the dwelling links the two bedrooms and allows light to flood into these spaces whilst still retaining the submerged appearance of the building. A pool of water will be added to this courtyard space to both provide assistance with temperature control, and also hint back to the site’s original use. The existing service hatches on the top of the reservoir will be retained as a reminder of the original use of this space, highlighting a touch of its industrial past. The existing mass of ground covering the front of the building will be retained, not only to continue reflecting its original function, but to help disguise the dwelling within the landscape and to be utilised as a thermal mass; a green roof also helping the building to blend with its surroundings. The second floor protrudes above the original reservoir height and, with black glass cladding, it both creates a strong statement and blends with the environment by reflecting its surroundings. Careful design has meant that natural ventilation, thermal massing and solar PVs are all able to be utilised within this building, creating a highly sustainable and environmentally friendly dwelling, utilising renewable energy technologies throughout.