This paper introduces the helioplastics theory published in 1962 by the Polish architect Mieczyslaw Twarowski. Through this theory, we aim to highlight both the historical and the utopian dimensions of the relationships between art, environment and the city: historical, because Twarowski’s proposals have to be understood in the context of the “radiant” modernity; utopian, because through his experiments, Twarowski expresses his belief in an urban solar enchantment. By contrast, we outline what could be a contemporary urban aesthetics of solar fluxes, likely to reconnect us with the fundamental sensory values of urban sunlight.