- Start at Penn Station. This is where Marlo Stanfield intentionally gets himself arrested (I think in season 4), thus confirming the wiretap that Prop Joe warned him about.
- Drive south to City Hall. Several scenes throughout the series take place outside of City Hall, including a brief sequence in the opening. Across from City Hall, you'll see the veteran's memorial steps where Stringer Bell and Prop Joe convene so Joe can warn Stringer about police surveillance (after Cheese gets detained after the dogfight).
- Drive south to the Inner Harbor. This is where Omar meets Stringer Bell at the end of season 1, trying to get Stringer Bell to talk about the Barksdale organization on tape.
- Head east to the Broadway Market, where McNulty's kids follow Stringer Bell.
- Head north on Broadway to see The Ritz, which in season one is Orlando's strip bar.
- Head east to Canton Waterfront Park, home of the Baltimore Police Marine unit, where McNulty "rides the boat" in season 2.
- Head east on Boston Street to see the Port of Baltimore, the focus of season 2.
- Head northwest to Patterson Park, where Prop Joe meets with members of The Greek's organizaton.
- Head east to Collington Square Park, and commence following the City Paper's Wire Tour, which covers several awesome sites from seasons 1-4, including Hamsterdam. My favorite stop is #5, Marlo's outdoor meeting spot, but seeing the rim store where Marlo hangs out is pretty awesome also.
- After leaving stop #7 on the City Paper tour, also visit Greenmount Cemetery, site of numerous meetups and interesting scenes.
This tour is very light on west-side locations. If anyone wants to expand this itinerary, I would look at these sites:
- The Independent's Wire Tour
- Mapbuilder The Wire mashup [has a ton of shooting locations]