Consolidating a library within the old patio of a building that for more than 100 years has undergone constant transformation is a challenge. Putting a roof over an area that was clearly defined to be open and under it a large library is a great opportunity. Due to its large area, a discussion was opened about implementing light on the surface of the ceiling, in a subtle and abstract way, aligned with the environmental parameters of the city. The white ceiling that appears to be suspended but is supported by large windows then became a White canvas for a play of lights brought on by daylight during the day and electric light for the long hours of darkness. Through qualitative and quantitative methods such as meetings, observations and surveys, the perception of the users was evaluated, and after tests, models and digital analysis, an intervention was defined on one of its facades that allows that ceiling to be reconnected with the natural and especially with the light. Exploring with elements such as the use of color or the management of reflections results in simple elements that can also be implemented from the architectural design, as support for lighting design.