Hi Damiano,
Good, that looks to be the issue I kind of expected to see. You are currently in the visual editor (Visuale). When making things in that editor, it does not compute HTML. It just basically writes exactly what you wrote. The bold text (<strong>) is achieved by using the icons on top of the editor (the [B] in this case). Like one would do in for example microsoft word.
To be able to use HTML and have it processed as HTML code, you will need to be in the text editor (Testo).
Go ahead and cut (or copy) your google maps iframe from your visual editor. Click to enter the Testo editor and paste it back there. See if that solves it.
With kind regards,
Kevin