If you visit Venice Italy, chances are very good you will work your way to St. Mark's Square ( Italian - Piazza San Marco ) and then visit St. Mark's Basilica ( Italian - Basilica di San Marco ).
St. Mark's Basilica is a free church to enter, and as it in the most crowded area of Venice, the line to enter takes about 15 or 20 minutes to get inside. As with many of the Catholic churches in Italy, there is a dress code to enter. Woman must have their shoulders covered, and shorts aren't "technically" aren't allowed. But that said, if the shorts are knee length there doesn't seem to be a problem entering as most everybody is wearing shorts because of the 90 degree heat and 80% humidity that is Venice during the summer months.
If you do visit the church, you might also want to visit the museum on the second floor. The entrance is on the right side of the church just as you enter. Look for the sign that says "Museum / Loggia" and climb the narrow set of stairs to the 2nd floor where you pay. The price when I visited was 5 Euros.
There is a book and souvenir store as you enter, and this second story view of the church. In the bottom middle of this photo you can see where the free visitors toured the church. There is no time limit in the museum and it features something most people are always on the look out for, the being restrooms. They are located way in the back off to the side.
Entrance to the museum also gets you access to the 2nd story roof and balcony with splendid views of St Mark's square and the Grand Canal.
Location: Saint Mark's Basilica Basilica di San Marco.1/20; f/5.6; ISO 1600; 17.0 mm.