Vintage lovers!
The Planetarium of Milan, Civico Planetario "Ulrico Hoepli", is a building located at the entrance of Giardini di Porta Venezia. It's a beautiful structure designed by Piero Portaluppi and commissioned by the Italian-Swiss publisher Ulrico Hoepli.
Also the interior design is beautiful, there you can find a planetarium which projects and represents the image of the stars and their movements in the sky.
The Planetarium also has a library which is a section of the Museum of Natural History, near by.
They also organize educational activity concerning astronomy as talks, events and even concerts.
I consider e/c natural wine shop a hidden treasure in Milan. Inside a building with an "Emergency" (that is actually an ONG) plaque outside, the first thing one might think is that is a hospital. Once passing the wall, there's a cute internal square, with Basilica di Sant'Eustorgio view. You can sit both inside or outside, which a strongly recommend for spring and summer days. A nice place for just passing by to grab a bottle of wine and drink it at home, having a glass of wine (they have many options) or enjoying a relaxed evening.
Flowers lovers! Orto Botanico di Brera is an hidden treasure right in the center of Brera and near by Pinacoteca.
The garden is a university and museum, there they organize events and activities for the public and schools. It has an amazing collection of flowers and medicinal plants, plus little corners where you can stop by and enjoy the silence for a bit.
Rotating modern art exhibitions in a complex of. beautifully design/renovated buildings, designed by Rem Koolhaas. Also has a great cafe and restaurant.