Tram
With tram 29 and 30 you can make a beautiful sightseeing tour through the city. At the Piazza della Repubblica you can hop on and it will take you on a tour around the center along the Stazione Porta Garibaldi, Cimitero Monumentale (this cemetery is worth a visit), and many other sights. It takes about 1 hour without the stops.
Theater/opera Scala
Now it’s closed due to restoration but it will be open again in 2005. http://www.teatroallascala.org (also see sightseeing) Teatro Manzoni
It’s not the Scala but this theater is also very worthwhile. It’s a good alternative now the Scala is closed. http://www.teatromanzoni.it