This is the proposed post on Harpa. As I told you last week, when we had a look at the outside at night, I take you to the inside now.
The mantle is made from a very special kind of glass:Dichroic glass
This kind of glass interacts with the changing daylight. The different angles of the lightfall, the different frequencies of the light at different times make the glass reflect parts of the light in the complementary color or let it pass to the inside.