As for Venice, since it's your first time, you will not want to see just the backstreets.... I'd recommend you to spend most of your time around Piazza S.Marco,instead.After all,this square used to be the center of a cultural and economic empire,and one that had many exchanges with the Far East,too. As someone already said,I'd suggest you to walk from the train station through the right bank of the Canal Grande and stop at Chiesa dei Frari and Scuola di San Rocco.In these very close to each other places you will see masterpieces of two great Venetian painters :Giogione and Tiziano.Then head to Piazza S.MArco and definitely visit S.Marco basilica and Palazzo Ducale. If you still have time visit one of the museums that have extensive exhibitions of the 18th century Venice art and crafts:Ca'Rezzonico or Galleria dell'Accademia. You will be then ready for a walk back to the station through via S.Marco and Ponte di Rialto.

In Rome, there are many things to be seen,and you can't get disappointed by any of them,so follow your inclinations and enjoy. For lunch,I would recommend traditional,simple roman trattorias,one for all Sabatino in front of Sant'Ignazio church.

Selamat jalan! Leonardo from Italy