I was wondering how they managed to get 'sunshine' into the tunnel. http://www.euronews.net/2011/09/16/belgians-trial-green-cement-in-tunnel/ http://www.euronew

I was wondering how they managed to get 'sunshine' into the tunnel. http://www.euronews.net/2011/09/16/belgians-trial-green-cement-in-tunnel/ http://www.euronews.net/2011/09/16/belgians-trial-green-ceme.... Spoiler => UV lights.