Getting from Milan Airport to the city

Part of the trip, I flew into Milan airport. When I got out of the airport, I looked for a train sign to go sightseeing in Milan before going to my accommodation. The airport is not complicated. The building is a single floor. The train station is a little separated from the passenger terminal. The train into the city is the most convenient way. But on the way back, I tried the bus to the airport, which was also convenient. It passed through a vertical forest, which is a tall building with trees planted on it. It looked green all over the building. There is only one like this in the world in Milan.