Sul or al

In L2 Italian lesson 8.1 Renting a car, Roberto says ‘Andiamo sul Lago di Garda.’ Why use sul, why not say ‘al Lago di Garda’? 

Hi johnnorthrop549, 

Thanks for your question, it's actually a great thing to notice!

Saying “al Lago di Garda” would be correct, however it is often used “sul Lago di Garda”, as you noticed. My best explanation for this would be that “sul” gives the idea of staying “on” the shores of the lake and/or in the lake area (as Lago di Garda in this specific case is huge). 

However, please note that this is not a fixed rule, and I've always heard it in relation to big/popular lakes (e.g. Lago di Garda, Lago di Como etc.). In fact, you wouldn't say “questo fine settimana andiamo sul lago” (this weekend we are going to go “on” the lake), but rather “al lago”.

Hope this helps! :)