On Tuesday, we featured the 105th challenge to see how well you knew the Metro system. Here are the answers. How'd you do?

This week, we got 39 guesses. 19 people got all five. Great work, everyone!

Image 1: Brookland

The first image shows the platform pylon and Red Line bullet at Brookland station. There are a couple of clues visible here. The mirror at center-right should tell you that this is a station with a curved platform. There are only two of those in the system, and those are the only stations with convex mirrors like this. Brookland and Silver Spring are curved due to their location between the CSX tracks, which are going through a gentle curve at each location. Another clue is the “RO” you can see reflected on the pylon. They're part of the “Brookland” sign that is painted on the development just west of the station. The Monroe Street bridge is also visible.

32 knew the answer.

Image 2: Columbia Heights

The second image shows directional signage on a pylon in the mezzanine at Columbia Heights. You could have solved this one several ways. First, the vault at Columbia Heights is a slightly modified Arch II design. The acoustical panels in the coffers at the top of the arch are not recessed as they are at all the other Arch II stations. The vault is also a little flatter.

Additionally, knowing the location of the mezzanine is useful. At all three of the other Arch II stations on the Green Line (Georgia Avenue, Mount Vernon Square, and Congress Heights), the mezzanine is at the south end of the station, meaning trains to Greenbelt are on the right when looking from the mezzanine into the trainroom. Only at Columbia Heights is the mezzanine on the north side and therefore the Greenbelt track to the left.

29 figured it out.

Image 3: Pentagon City

Pentagon City is our third picture. This view shows a mezzanine pylon directing passengers to the inbound platform. There are only two Blue and Yellow stations with side platforms, so you should have been able to easily narrow this down to Pentagon City and Crystal City. But there is one difference between the two stops: The arrangement of the mezzanines.

Metro's underground side platform stations have their escalators arranged like a tuning fork (sort of like the letter “Y”). In virtually every case, the mezzanines have a dual tuning fork arrangement. That looks something like this: [:::::::::::::>>]. In the picture, you can see that there are actually three tuning forks in sequence like so: [:::::::::::>>>]. There are only three locations with three tuning forks in sequence: Pentagon City, Ballston, and L'Enfant Plaza (7th & Maryland entrance).

Crystal City does actually have three tuning forks, but they're not in sequence. One is reversed, like this: [:::::>><::::::].

34 of you guessed correctly.

Image 4: East Falls Church

The fourth image shows a view of the sunset at East Falls Church. This is the only outdoor station that is shared by the Orange and Silver lines. All of the other shared stations (from Ballston to Stadium/Armory) are underground. Other clues included the eastbound traffic on I-66, since this is a median station, and the high-voltage power lines which run along the Washington and Old Dominion Trail right-of-way.

37 got it right.

Image 5: Waterfront

The final image shows the stair and elevator at Waterfront station. There are only two stations with Waffle style vaults that are only on the Green Line: Waterfront and Navy Yard. At Waterfront, the east end of the mezzanine ends with a stair adjacent to an elevator. At Navy Yard, both mezzanines end with dual escalators. The elevators at both Navy Yard mezzanines are embedded; they descend through the floor of the mezzanine, rather than being at one end of it.

34 came to the correct conclusion.

Thanks for playing! We'll be back next week with week 106.

Information about contest rules, submission guidelines, and a leaderboard is available at http://ggwash.org/whichwmata.

Matt Johnson has lived in the Washington area since 2007. He has a Master’s in Planning from the University of Maryland and a BS in Public Policy from Georgia Tech. He lives in Dupont Circle. He’s a member of the American Institute of Certified Planners, and is an employee of the Montgomery County Department of Transportation. His views are his own and do not represent those of his employer.