City of Boston Planimetric Map

Here's a map (PDF link) you might find helpful, especially with the stair locations.

If you zoom in close enough (onscreen) you can see some measurements, too. Prepared by the Boston Redevelopment Authority. Property information is courtesy of City of Boston Assessing Department. Sidewalks and building footprints derived from Boston Water and Sewer Commission 1994 digital orthophoto project. NAD 1983 State Plane Massachusetts Mainland FIPS 2001 (Feet). Parcel information from Assessing Dept. - FY2010 (Jan.1, 2009) Note: Greenwy parcels have not been updated.

Note: I'm told the map needs to be printed at 24" x 36" for the scale to be right (1"= 100'-0").