The Castle of Hostalric was a point of surveillance and defense with a territorial purpose. Now it can be an experimental Observatory to face the climate emergency. It will become an active and useful center without ceasing to be visited. The fortification has a dominant position over the territory and lives on the resources generated in it. It is a defense element designed, at the time, to be able to live self-sufficiently during periods of siege.

The proposal reinterprets the Castle as an Observatory and a space that houses advanced institutes that investigate sustainability, the closing of cycles and the circular economy in the cycle of water, materials, energy, waste, mobility, territory, etc. A project that reinterprets self-sufficiency and the limitations imposed, at the time by the sites, in the need, now, to face the climate emergency. A reduction in consumption and an increase in efficiency are required, seeking to cover needs with minimum consumption.

It is proposed to create an advanced technological center capable of generating knowledge as well as being a "nursery" for companies, linking advanced level research with practical replicability in the territory. That is to say, that he is exemplary in how he himself reaches self-sufficiency and circularity of resources, generating enough knowledge so that these good practices can be extended. In this sense, the space will have natural and active systems that are pedagogical for the visitors. The visits are stimulated with activities and also by the very characteristics of the place, which can be interpreted as a door into the territory and as a cool climatic refuge in hot summers. In the short term, the fortress is an advanced study and research center.