St. Croce church Florence, Italy
This church looks very simple and unassuming from the outside, however on the inside its a whole different story. The art inside is beautiful, its very large, one cannot tell from the outside this vast space exists on the inside. The entrance is free also to the museums, galleries, tombs and other small chapels, which is different from most other places in Florence where you have to pay for everything.
There are volunteer guides inside which give you as much information as you need, and are more than willing to tell you more if you ask. The galleries and museums have amazing paintings, and the church itself contains tombs for famous persons such as Michelangelo, Galileo, and Dante.
On the outside the monastry has a nice walking area and the ambience is simple wonderful. I highly recommend you visit this place when in Florence.