The power pylons by Hietasaari, the “main” beach in Helsinki, were designed by Antti Nurmesniemi and are lit up until Jan 6th by Helsingin Energia. If you want to see the lights, you may want to time your visit better than to go there during the few hours of daylight as we did. Apparently it looks great though, so we might be back.
Free But Fun 
Very interesting!