If Thucydides is

North of Xenophon

- In 1774, Horace Walpole sent a letter to Horace Mann that included the following line: "The next Augustan age will dawn on the other side of the Atlantic. There will, perhaps, be a Thucydides at Boston, a Xenophon at New York."  This line of Verse 3 is probably a reference to that quotation, telling us to look in the Boston area.

- This could also be a reference to the names carved in the exterior wall on the east side of the Boston Public Library, but while the name "Thucydides" is higher on the wall, it's actually south of "Xenophon" in that arrangement.

Take five steps

In the area of his direction

- "His direction" would probably mean "west," given the context of the Walpole quotation.

- The "five steps" seems very specific, but it isn't clear whether these are literal or metaphorical steps.

- If the "steps" are city blocks and the Boston Public Library is the starting point (because "Thucydides" and "Xenophon" are carved on the exterior wall), it's possible that we are meant to go west from there.  Going west five blocks on Boylston from the corner of the library would put one (very roughly) at the corner of Boylston and Fenway, near the Boylston Street Bridge over the Back Bay Fens.

- If the "steps" are subway stops, the Kenmore MBTA station is five stops west of the hub of the Red and Green lines.  This would make sense with the T-shaped perch for the bird in Image 11, but it isn't clear why we would start at the Park Street hub.

A green tower of lights

In the middle section

- This is likely to be a reference to the famous "Green Monster," the left field wall at Boston's Fenway Park.  The park is due west of the Boylston / Fenway intersection, only a few hundred yards from the Boylston Street Bridge. There are several large sets of stadium lights that rise from the Green Monster.  They are some of the tallest structures in the immediate area and they were visible in all of the Back Bay Fens before construction blocked some views over the last decade. The lights are still visible in most of the area today, and would definitely have been visible in the 1980's.  Here's a view of the "green tower of lights" from the Charlesgate overpass over the turnpike:

- Searchers have sometimes suggested that "green tower of lights" could be a reference to the green lamppost beside the "Two Circles" structure at Charlesgate Park.  Unfortunately, Google street view only shows the structure appearing after a major cleanup of the area sometime between 2007 and 2009.  The interpretation cannot be correct unless a similar structure was in the area earlier and removed prior to 2007.

Near those

Who pass the coliseum

With metal walls

- The only good match that has been proposed for "the coliseum with metal walls" is Fenway Park.  The famous left field wall, the "Green Monster," is made of metal.

- The phrasing of "those who pass" might refer in some way to the route of the Boston Marathon.  The marathon goes up Beacon Street to Kenmore Square and then turns onto Commonwealth Avenue.  Those locations match many of the visual references in Image 11.

Face the water

Your back to the stairs

- These lines appear to tell us that we should be looking for a place where there is a flight of stairs near water.  Based on what we know about Image 11, "the water" in this case would most likely be the Muddy River, which flows through the Back Bay Fens and Charlesgate Park.

- There is a staircase that connects the east end of the Boylston Street Bridge to Mothers Rest, but those stairs cannot be the ones described here because the staircase was only constructed in 1998.

- There are four very short sets of stairs at the World War II memorial near the rose garden.

- The most likely sets of stairs are at the Two Circles area.  There are three possibilities:

• One set is on the far side of the pumphouse, going up to the door.  This spot is highly unlikely because of the risk of hitting underground cables or pipes.
• Another set is at the entrance to the first circle from the sidewalk.
• The third, and most likely, set of stairs is where the two circles meet.  Facing the water with your back to this set of stairs would put you in the notch between the two circles (middle- to lower-right in the picture below).

- This is most likely a reference to the song "Dirty Water," recorded by the Standells in 1966.  The song's refrain emphasizes the line "Boston you're my home."  According to Wikipedia, the song "is beloved by the city of Boston and its sports fans."  The reference to "Dirty Water" would be particularly appropriate for a site along the Muddy River.

- This could also be a vague reference to Mothers Rest (if home is considered a place where a mother would be "at rest"). 

All the letters

Are here to see

- This could be a reference to the Back Bay Fens Victory Gardens where the paths are labeled by letters of the alphabet.  The Victory Gardens are directly across the water from Mothers Rest, but are not visible from the "Two Circles" structure or the WWII memorial.

- Facsimiles of the letters (not the originals) between Walpole and Mann are available at both the Boston Public Library and at Harvard (and possibly other university libraries in the Boston area as well). Bound reproductions are available at many libraries. 

Eighteenth day

Twelfth hour

Lit by lamplight

- Reference to Paul Revere's midnight ride, which occurred in Boston on the 18th of April in 1775 and was guided by lamps hung in the Old North Church.

- The reference to "lamplight" might be an indication that the casque is buried near a lamppost.

- The final line is so vague as to be almost meaningless.

- This could be a paraphrased version of the biblical quotation, "Ye shall know the truth and the truth shall make ye free" (John 8:32).  As such, it could be an indirect reference to the presence of that biblical verse on the 1881 gate beside Phillips Brooks House at Harvard. 

- "Veritas" (truth) is the motto of Harvard, so this could also be a reference to the school itself or to the Harvard Club of Boston, located just east of the 2C site.

- "Truth" and "be free" could be a reference to Sojourner Truth, a freed slave and abolitionist who visited Boston.

There are at least three written works that use the words of this line as part of a verse:

1. "In truth be free" is a line from an 1864 anti-slavery song called "Ode on Washington's Birthday."  The longer quote goes like this:

     Burst the fetters of oppression,

     Let our land in truth be free,

     And no longer Slavery's curse

     Blast the land of Liberty.

     On to victory!

   If this is a reference to that song, it could be intended as a hint toward the Back Bay Fens Victory Gardens, or it could be intended as a hint toward the statue of Victory that is part of the WWII memorial.  The Victory statue is the same one represented by the woman's flaring hair in Image 11.

    

2. "In truth be free" is also a line in a poem called "The Coming Age" that was written by Dwight Marven.  The poem was published in Boston in 1908 as part of a truly bizarre book called "Gillette's Industrial Solution: World Corporation."  An earlier line of the same poem says that "The earth will yield its fruitage to the hands that give the toil."  This might also be a reference to the Back Bay Fens Victory Gardens.

    

3. "In truth be free" also appears in "The Spirit Voice" by Charles L. Reason.  The relevant stanza is as follows:
   

     The captive in his hut, with watchful ear,
     Awaits the sweet triumphant songs to hear,
     That shall proclaim the glorious jubilee
     When crippled thousands shall in truth be free.

   Nothing in the poem itself seems tied to a location in Boston, but the poet's first name could be a (very weak) connection to the Charlesgate area.