Tropical climate areas have an advantage in terms of utilizing natural lighting for buildings. On the other hand, deep plan buildings have limitations in natural light penetrations through the sides of the building, while making the natural light enters from the roof risks of blending in with the heat and glare. Cultural heritage buildings are an inheritance that must be preserved and protected. Nowadays, some of them switch functions to be managed as public functions. Cultural heritage buildings with deep floor plans have double problems, specifically their limitations in natural light penetrations from the sides of the building, and also how to maintain the visual appearance of the building as much as possible when renovations are being carried out. This paper aims to explore strategies that can be done to improve natural lighting in the cultural heritage buildings with a deep floor plan. A case of study of cultural heritage buildings was also used in this research to provide a description of specific natural lighting techniques that can be applied. Field measurement methods and digital simulations are used to determine the existing natural lighting conditions of the study object and provide a visualization of design recommendations. The results show that vertical lighting can be used in cultural heritage buildings without changing the building façade. This strategy is carried out by minimizing the incoming glare through the consideration of the vertical angle of the sun's shadow, as well as the reflection of light to maximize the light distributions in the building.