Matanuska Glacier itself is a wonder to see. It's supposed to be one of the only glaciers you can see up close in Alaska from the highway. If that's all you're interested in then stay on Glenn Highway for some great distant views of a 4 mile wide and 27 mile long glacier. There are several pull off points along the highway for sightseeing. If you'd like the chance to hike to it and/or on it then drive into Matanuska Glacier Adventure. It's a little on the pricey side as others have mentioned but, it could be a your only chance to do so.

Awesome view with good short trek. The road to this place is private so be ready to shell out 30$ per person if you want to explore on your own else go with tour group and pay 100$, they will provide nice gears to trek further. Restroom facilities is there in office. It takes minimum of two hours to trek to shortest place and get some nice clicks. This place is a must visit.