Pantheon - one of the most remarkable buildings in Rome - can be visited free of charge.
Window shopping is one of the most popular attractions in MIlan - and free of charge unless you decide to enter and spend your money on actual shopping. Galleria Vittorio Emanuele II is a must to visit place.
Piazza S.Pietro in Vincoli 4/a.
La Scala offers several free events each month:
Palazzi dei Rolli is a unique concept of Genoa from 16th and 17th century when palaces and mansions of noble citizens of Genoa were listed in Rolli, and according to this listing owners of the palaces had to serve their city by providing accomodation to statesmen and nobel guests viting Genoa. Today 42 of those palaces are gathered under the protection of Unesco, and many of them may be visited free of charge as they are housing shops, banks, offices etc. Palaces are mainly located on Via Garibaldi and adjustant streets.
Basilica San Miniato al Monte is considered as one of the most beautiful Romanesque buildings in Tuscany with extraordinary and unusual interior. Located behind Piazzale Michelangelo with exciting views over Florence. Every evening at 17:30 you can admire here monks chanting.
Loggia dei Lanzi also known as Loggia della Signorina was built between 1376 and 1382 and is located just next to Piazza della Signorina. It consists of wide arches open to the street and exhibits sculpture gallery of antique and Renaissance art. The most famous is the bronze statue of Perseus by Benvenuto Cellini.
No doubt that central point of interest in Basilica of Sant'Ambrogio is its imperssive altar - made in gold, gilded silver, precious stones and enamel, is a true masterpiece of Carolingian goldwork.