a piazza

I'd like to understand why the phrase is 'andiamo a piazza', but 'andiamo alla catedrale'. Why don't we way 'andiamo alla piazza'? Also in that lesson about Firenze it seems misleading to translate duomo as cathedral and catedrale as church. In my dictionary the word for church is chiesa, and duomo is the dome of the cathedral. Are catedrale and chiesa interchangeable? or are catedrale and duomo interchangeable? Sorry for so many questions, but this lesson presented me with a lot of questions. Grazie.

ciao,non sono sicuro ma credo che il duomo sia la piu` importante chiesa in citta`e la catedrale sia il siede del vescovo. Quindi,tutte catedrali sono i duomi ma tutti duomi non sono le catedrali.! a dopo martin

Cari Adriana e Martin, here is my reply, in English! Martin is right regarding the difference between Duomo and Cattedrale, it is a religious subtle difference, all about the Bishop, and not about the style of the building. Martin one thing that you cannot do is change the word "Duomo" into plural! While you can with "Cattedrale/i. The "dome" on top of many cathedrals in Italian is called "Cupola". Andare a... Regarding "Andare a Piazza Navona", for example, is right only if we put the name of the Piazza in the sentence. Otherwise is preferable to use the prepositions: in or alla as Adriana pointed out. Italian prepositions are a difficult topic because they sometimes match the English prepositions, but other times they don't. In Italian their use come from Latin and the rules are quite obscure, for example we use "a" in front of a name of a city or a small island: andare a Roma, andare Capri ..But if the island is big we use "in": andare in Sicilia, andare in Sardegna How big is big? How small is small??? In is also in front of a region or a country: andare in Toscane, andare in Italia. Ciao a tutti e buono studio!