Whether you take the 45 minute walk through town from the train station or arrive by taxi, the Field of
Miracles (Campo dei Miracoli) takes you by surprise. One minute you are in small, crowded, and rather dark city streets, and then suddenly the vista opens up and in front of you is a huge expanse of green
grass with a bevy of magnificent white marble structures, including the famous Leaning Tower, the huge round Baptistery, and the grand cathedral (duomo).
All the Campo's buildings have facades of brilliant white marble, and rows of delicate 
arches and columns. Unique to Pisa, this lovely architectural style is called Pisan Romanesque, and is much lighter, and more elegant than the thick-walled, ponderous Romanesque buildings found elsewhere in Europe.
The Campo has always been the center of life for the citizens of Pisa. For centuries they were christened in the Baptistery, married in the Duomo, recognized for their achievements in ceremonies at the Tower, and buried in what has been called the most beautiful cemetery in the world.
Besides these religious sites, there are a couple of museums. The Museo dell'Opera del Duomo houses Pisan paintings and sculpture, as well as treasures from the cathedral and some ancient Egyptian, Etruscan, and Roman artifacts(the town was once a Roman settlement). The Museo delle Sinopia displays some of the original wall sketches for the frescoes seen in the cemetery.
You can purchase tickets (in a somewhat confusing scheme) for some or all of the buildings and museums, although a special ticket and reservation is required if you want to climb the Leaning Tower. I think the cathedral and Baptistery are well worth seeing--both are impressive and contain magnificent carved pulpits. The cathedral interior is a stunning mix of early Christian, Byzantine, and Islamic motifs. The Duomo Museum is also worth a look if you have time and are interested in Pisan art.
Hundreds of souvenir stands line the streets surrounding the Campo. Buy a little Leaning Tower here, if you must, but don't waste time searching for treasures. These stands are full of the tackiest bits of overpriced junk you'll ever come across.
