The architects of the older cathedrals in Spain knew how to harness the power of light, by refracting the light through their windows and spot-lighting the alters at different times of the day.
The cathedral in Santiago de Compostela.
A cathedral in Madrid.
A cathedral on the Sacred Shore of the River Sil. For more about this challenge: http://dailypost.wordpress.com/dp_photo_challenge/refraction/