Let's see...
There is a doll museum in Bellevue - always good for your creepy doll stories:
http://www.dollart.com/The Aurora Bridge (the one with the Troll) is also known for a high amount of suicides. I used to work right there under it - our parking lot was a favorite target for jumpers. That area (Fremont) also has a Rocketship on a building, a statue of Lenin from Russia and refers to itself as 'the Center of the universe'. The Summer Solstice fair is there every year (obvious Summer gathering).
The Labyrinths, yeah, they are frickin' everywhere around here...
There's a high number of crows in the north end (one of my players actually printed out a map of sightings).
Everyone talks about the Wet Spot, but there is also a known gang in the area called the Street Mobb (two b's) that is pretty involved in prostitution. Mobb stands for Money Over Broke B**ches.
Out in Redmond area is a retreat called the Longhouse. Private retreat with standing stones and camping area, plus a building with an indoor pool.
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Over all, the themes that came up in both Seattle games I am running is that the ever-changing and erratic weather is a sign of a back and forth of the Fae courts.
However, both groups also seemed to come up with the idea that there is a malaise in the area, that there is a high degree of apathy. In one game, there's something in the Underground that is ancient that spews out a miasma of apathy and depression. In the other, it's a sort of stalemate between the Fae courts since all of the Fae actions cancel each other out. That's lead the local courts to being sort of tense but ineffectual.
Another common theme is that Seattle, being such a high tech area, isn't very hospitable to wizards. Neither have a strong White Council presence.