A lot of the Cascade range is basalt, and you don't need to cut down very far to expose it. A result is that most waterways in Oregon have revealed a lot of basalt around them, at least in the mountains.
Climbing on columnar basalt is interesting. Vantage / Frenchmans Coulee (2 hours or so east of Seattle) has a bit of a bad reputation but some of the routes are decent.
Pilot rock outside of Ashland you can even hike to the top
It's rare to have basements where I live in Bend, because it's all lava rock right under our feet, which is really expensive to remove.
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Yep, there's a ton of it to be found especially in the Columbia River Gorge. For anyone not hip to Nick Zentner, allow me to introduce you to this national treasure...
https://www.youtube.com/watch?v=VQhjkemEyUo
https://www.youtube.com/watch?v=YSi17xJB1Sg
https://www.youtube.com/watch?v=0IjLO9ABKYU