[TangerZ]

I was born in Lethbridge and moved to Calgary when I was a kid, but I've been back once, anyways, you could:

1. As others mentioned, you could go to Japanese gardens. I went last year, and they now charge a $7.00 admission fee (it was free back in the day). It's cheaper if you have a group of 10 or more. There are also guided tours available, but just going around yourself probably won't last for more than a half hour.
2. Go to Henderson Lake off of Mayor Magrath (or is it Mcgrath, I dunno) Drive, adjacent to the Japanese garden. There you can enjoy a lunch at a picnic table along the walkways, or even rent a peddle boat or canoe at the boat rental shop there. Unquestionably the most scenic, relaxing place in town. Very similar feel to the lake area in the middle of Kelowna if you've been there.
3. Go on a day trip south to Waterton National Park and enjoy the lakes and wilderness...approx. 1 hour drive south. They have a small village there with shops and a restaurant or two, open fields for something sporty nearby, and boat tours on the lake, and just wilderness.
4. hmmm, not much else to do in Lethbridge, downtown is pretty small. There was a restaurant we frequented called Buffalo Bills back in the day, but it's gone. Sadly, I can't recommend much else, as I haven't been to their museum or theatre. A buddy of mine would recommend dorm parties at the University of Lethbridge, but that doesn't help unfortunately. :P
*5. Oh I just thought of a good restaurant. It's O-Sho Japanese restaurant if you like Asian cuisine. Nice decor, and big menu.