The Back Bay is bordered by the Charles River to the north, the Public Garden to the east, Fenway-Kenmore to the west, and the South End to the you guessed it south.
By bus
Routes CT1, 1, 9, 10, 39 and 55 service the area. The 1 bus is the most useful to tourists, as it runs on Mass Ave and connects the Back Bay with Central and Harvard Square in Cambridge.
By car
Like most of downtown Boston, driving in the Back Bay is a terrible idea. While, unlike the rest of the city, the streets are laid out in a grid, the traffic tends to be bad to terrible. Newbury is the worst, as trucks frequently double park and pedestrians brazenly walk in front of cars. Boylston and Mass Ave are also frequently congested. If you must drive there are several parking garages in the area, and Exit 22 off I-90 East only serves the area. Storrow Drive is also another point of egress, although during rush hour it is often gridlocked.
By train
The Back Bay station is served by Amtrak trains, and by MBTA commuter rail Attleboro/Providence, Framinghham/Worcester, Needham, and Franklin lines.
By Subway
Orange Line: the Back Bay station is near the border of the South End, near the Copley Place mall and the Prudential Center. Also served by the 10 and 39 buses.
Green Line: Several stations on the Green Line are located within Back Bay. The Green Line splits into multiple branches here: the following listings will indicate which branches serve which stations.
Arlington
[all branches]: In the far corner of the Public Garden, by the more 'ritzy' end of Newbury St. Also served by the 9 and 55 buses.Copley
[all branches]: Near Copley Square, the Boston Public Library, Trinity Church and The John Hancock Tower. The last stop before the E branch forks off. Also serviced by the 9, 39, and 55 bus. There is no crossover or transfer between the inbound and outbound platforms: to transfer between inbound and outbound trains, ride to Arlington and transfer there.Hynes Convention Center
[B, C and D branches]: Actually on Mass Ave, the Convention Center from which it takes its name is a few blocks away on Boylston St. It serves the more 'artsy' end of Newbury st, as well as the Prudential Center, Boston Architectural College and the Berklee School of Music. Also served by the 1 and CT1 bus.Prudential
[[E branch]: Next after Copley going outbound. Connects directly into the Prudential Center, but for convenience most residents use nearby Hynes and walk, as the E has the most infrequent service and it is easier to get to most destinations on the other lines. Also served by the 39 and 55 bus.