The marine area in Amsterdam, currently only partially publicly available, needs to be reintegrated into the public space. To start the reintegration process, a swimming pool and spa, which both meets the identity of the area and the vision of the municipality, will be added to this area. A new central route is placed through the marine area on which the building is situated, activating the surrounding area. Swimming pools are notorious large energy consumers. To overcome this, the building is designed with a focus on reducing the energy demand and using sustainable energy sources only. Orientation and the organization of the building are used to gain as much energy from the Sun as possible. A conservatory on the south side with a large swimming pond to capture this solar energy. The conservatory is both a public space and part as the park as well as part of the building. A rammed earth wall is introduced in this conservatory to store the collected thermal energy from the Sun. Moreover, rammed earth is able to absorb large amounts of humidity and is therefore placed adjacent to the pool, reducing the energy for ventilation requirements. All infrastructure of this building is situated in this central wall, where it becomes the backbone of this building; transporting energy, water, heat, air, and people. The wall in combination with the other elements provide an adaptive and natural indoor climate for the building. Installations, such as heat pumps, are only used to provide additional heat/cooling when it is needed. The roof of the building situates a garden and pavilion where guest can escape the busy city of Amsterdam when they are in the spa. The roof of the pavilion has solar cells, and a pattern is created with open spots that creates a playful scene of shadows and light. The spa uses the existing structure of a building that is currently situated on the marine area. The old walls of the building are grinded down to fine pebbles and are made into the terrazzo floor. The interior of the swimming pool repeats the structural pattern of the old building. Inside, water streams from the higher hot baths to the lower colder baths and swimming pools just as in natural spa’s.