If someone was visiting your town for the first time, what would be the one place you'd tell them they just had to go see
That's a very good question. There is SO much gorgeousness in our area that it's hard to pick just one. Plus, we've done this kind of thing lots - our family loves to show off our area to out of towners, and we were so amazed for the first 5-10 years we lived here (I was 10 when we moved to WA) that we went and did these touristy things over and over and over.
If it's the right time of year (like now), I'd probably pick the Rose Gardens. They are amazingly beautiful, and there's a perfect view of Mt. Hood.
For people that I know well, I tend to enjoy taking people down the gorge to the Bonneville Dam, where they have a fish viewing room, and you can walk on the generators. It's a cool place to spend an afternoon walking and playing, and it's a beautiful drive there. If someone was really interested in hiking, they could stop a mile before it and go up Beacon Rock. And if they were wanting more, they could go around the gorge loop: go over the beautiful Bridge of the Gods another mile after the dam, then get yummy fries and ice cream at Cascade Locks and then see Multnomah falls and Crown Point on the other side.
If we had a little longer, and people hadn't been to the coast, Lincoln City is an amazing place to go to because it's right on the beach and oregon beaches are so different from say California. ;)
But really, the thing I tend to bring people from out of town to is restaurants. We have a lot of favorites, and even though they aren't all unique to our area, it's a fun time to sit together and laugh and eat. Old Spaghetti Factory is a good example of a restaurant that isn't just local, but a very good place to take out of towners because we have the very first one here in Portland (the purple roof one!)
I didn't do a very good job at saying "one place" did I? ;)
I had a post a year or so ago on my main blog with links to most of these place and it worked out well for enhancing this one heh!