Here's a hint: it's very close to...

Portland. In fact, it's technically part of the city. It was acquired by the City of Portland in 1960.

If you're familiar with Portland, chances are you've seen the outside of this landmark. But have you ever seen the inside?

Thanks to Google Maps, we can see it from an angle that many have never seen it.

So...what is it? Tell us your guess in the Facebook comments on the post!