This paper presents the case study of Guevara Tower, a historic building located in Ischia (Naples), investigated as part of the CHIARA project with the aim of preserving significant wall paintings. The research combines a historical and architectural analysis of the tower—originally built in the fifteenth century as a noble residence and subject to multiple restoration efforts—with a detailed monitoring campaign of its microclimatic conditions. Starting in November 2024, indoor and outdoor environmental data were collected using sensors placed in key decorated spaces. Parameters such as air temperature, relative humidity, VOCs, CO2, and particulate matter were monitored and evaluated according to Italian standards UNI 10829:1999 and UNI EN 15757:2010 for the conservation of cultural heritage. Results revealed frequent deviations from recommended relative humidity and temperature thresholds, primarily due to direct solar radiation, which exposes the wall paintings to potential degradation. The findings emphasize the need for continuous, site-specific environmental control, considering the acclimatization of artworks to current conditions. The study also highlights the necessity of further investigation into light exposure using dynamic daylight simulation tools, to assess photodegradation risks based on European guidelines. This interdisciplinary approach, grounded in scientific data, historical knowledge, and minimally invasive strategies, offers a model for managing environmental risks in heritage buildings and ensuring the long-term conservation of sensitive cultural assets.