The garden takes up an entire city block and was designed to replicate the garden of a sixteenth century bureaucrat scholar. (It's also considered to be the most authentic Suzhou-style Chinese garden outside of China, built in 2000 as part of a partnership between Portland and its sister city.)
I knew the garden was in the middle of town, but I still expected it to feel more separate. Tall buildings are visible above the garden's architecture and the sound of traffic was always there in the background. At one point the bass from someone's car stereo was almost as loud as the tour guide's voice.
Definitely take the guided tour if you happen to visit. There's symbolism in everything, and so much history about the garden and why it's the way it is. You could thoroughly enjoy the beauty of the place without knowing the details, but the tour adds a lot.
Another tip -- the brochure is worth reading. I'm always so busy keeping track of kids that I just put the brochure or map or whatever into my purse, but this one is really interesting. Even if it did take me a bit too long to figure out the interactive window feature.