The brick monolith is on a traffic island across from Eastern Mountain Sports.
When you start there, you get these answers, with the boxed letters
capitalized:

* Cross the street to an art gallery, advertising its next show as "frEsh to
  dEath". I don't know what that means, incidentally.
* The wall you encounter just after that has had most of its letters fall off,
  but what remains is the number 30 and "T E".
* The thing that costs about $4 million is "vErtical transportation
  improvEmEnt".
* Tonight's late show at the Brattle Theatre was "skaTetown usa".
* You go down the alley and turn right. When you come out into the open, you
  keep going straight into a small corridor, because no directions told
  you otherwise. You pass a door that says TO ENTER PLEASE RING BELL, so you
  fill in "to EntEr".
* This corridor forms a T-junction. To your left is Harvest, so the "yearly
  celebration" tells you to go that way. You continue straight for a fair
  bit after that, until on your right there is a sign for a candle shop, saying
  "We have absolutely no common scenTs!"
* The 'juice bar' is actually a power station for your "ElEcTric car".
* You cross through the Charles Hotel plaza, and emerge facing an actual
  monastery, so you can take that clue literally and enter the path to the left
  of the monastery. When you turn left without passing through the archway, you
  go around the perimeter of JFK Park. Across the street is a sign that says:

        <- Harvard Sq.
           No. Harvard St. ->

              OOPS
  
  The OOPS is made of stickers, apparently attached by a vandal who shares our
  taste in puns. The boxed letter is the T in "harvard sT".
* Without crossing the street, you turn left (toward Harvard Square). The nice
  smiling lady is the Mona Lisa, appearing on an ad for the Foundation for a
  "beTTer" Life.
* You pass an incongruously fancy Dunkin' Donuts, an anagram (Via Vai), and
  a public transit route (a restaurant called Redline). To your right is
  a crosswalk that's marked on the curb but not on the street due to
  construction. You pass parking spaces that say "Reserved 001" and "Reserved
  002", which is why we said they're reserved for Bond's predecessors. On the
  next block, you pass a Lutheran church, with a stone engraving in front
  saying that God is "in the midsT of The ciTy".
* The next direction you cross the street in is to the left, because it brings
  you toward Holyoke Center, which has windmills on the roof. At the other end
  of this street, the street sign informs you that this was "waTEr" St in 1631.
* The following directions have you turn left just before the Harvard Lampoon
  building (a silly place). On the traffic island is a monument to some
  journalist whose name I actually forget, but it has an E and a T in the
  appropriate places. He won a Pulitzer Prize, which takes second billing on
  the engraving to editing the Harvard Crimson.
* When you go up the hill, emerging at Mass Ave, and turn left, there is a
  fire hose connection near the ground. It says 'This Siamese "connEcTion
  sErvEs" 1300' and a few other street numbers.
* If you were to turn around and cross twice, enter an informative building,
  and use a computer, you'd be using the kiosk in the Harvard Bookstore. Their
  catalog contains a book called "The Lightning Man: The Accursed Life of
  Samuel F. B. Morse", cluing Morse Code. Apparently if you went there during
  BAPHL and searched for the exact phrase "lightning man" or "the lightning
  man", the result would be a *different* book entitled The Lighting Man
  that didn't show up for us a week before, and Samuel Morse would be nowhere
  to be found. We apologize.

The highlighted letters are all Es and Ts. In Morse code, E is a dot and T is a
dash. If you read the Es and Ts in each answer as dots and dashes in a Morse
code letter, you get INSTITUTIONAL.