4-hour tour in Helsinki – Capital of Finland

On October 18, I took my flight from Copenhagen to Tallinn, the capital of Estonia. On my way to Tallinn, I had 4-hour transit on Helsinki- the capital of Finland. On arrival, I was tired, but an idea came to my mind. Why not go out and see the Helsinki city since I am already here? Will 4 hours be enough for touring the city? Can I make it back to the airport for my next flight? Before answering this question, I would like you to change the time on…