One of the things that struck me the most the first time I visited Madrid was the Atocha Railway Station. It seems incredible but it is true, since I did not expect to find some sort of nice Botanical Garden there.
The station in itself is like any other, that is to say, it has hallways, boards indicating departures and arrivals of the trains and counters where one can buy tickets, but as soon as you go towards the exit, you suddenly find a huge space with a glass roof, full of plants. And these plants are not small, on the contrary, they are trees and huge plants as if they never ended.
It is surprising and a very pleasant place. It is usually full of people going for a walk or sitting down and relaxing while waiting for their train. The rest of the station is rather normal, even though I had the impression it is very well organized.