This loop is awesome! Took 3 days. I loved it! Seattle Park and Spray Park are incredible. Descending from Seattle Park to Carbon River was rough. Lots of bush-whacking and the trail is very primitive. Took forever and since we were descending it was hard on the knees. When we saw the wonderland trail sign I hugged it and wanted to cry. Ha! Blowdown at the river crossing right before Carbon River campground, so you have to cross the river. Also, you have to take the 1.1 mile upper crossing because the lower crossing is washed out. Be prepared for a huge suspension bridge. Also, Carbon River campground seems eerily abandoned... VERY primitive also. The most primitive sight we've seen on Mount Rainier. Going up Isput pass is very steep and a lofty hike on it's own. Lots of people camping at Mowich Lake. We were excited to take a swim after two long days of hiking! I would totally do this again and combine it with northern loop next time (northern loop is also really fantastic) The road to Mowich is really uneven and rocky. Takes a while.