In an aging population, the prevalence of people with dementia is increasing. Intelligent environments can offer a solution to support people in the early stages of dementia, who often experience problems with maintaining their day-night rhythm. The focus of this work is developing an Intelligent Environment for assisting these people with their daily structure while living independently at home. Three co-creation methods with several stakeholder groups were used to elicit requirements and develop a prototype of an Intelligent Environment. Participants were involved in sessions using Mind Maps (N=55), Idea Generation Cards (N=35), and in a multidisciplinary design team with representatives of eight organizations. The result of these sessions was a set of 10 requirements for the Intelligent Environment on the following topics: context-awareness, pattern recognition, adaptation, support, personalization, autonomy, modularity, dementia proof interaction, costs, data and privacy. Based on these requirements, several scenarios were developed to explicate such an environment for supporting people with early dementia. The design team translated the requirements to a real-life prototype of an Intelligent Environment integrated into a demonstration home. The prototype serves as a basis for further development of Intelligent Environments to enable people with dementia to live longer independently at home.