We did this mid morning on a Sunday. The trailhead is just inside the national park pay stations on the Ohanapecosh entrance. Parking was just barely full, but we were able to get a spot barely 1 minute from the trailhead.
The bathrooms at the trailhead were descent, not too crowded, and stocked with tp.
The trail itself is quite easy, smooth dirt 95%+ of the way through. There are quite a few sizable trees during this descent which are already amazing to see. You descend to the river level and reach a suspension bridge. This is how you cross the river to see the big trees. Only a few people can cross the bridge at a time(sign recommends 2 , though many groups did more than what was suggested). This is where we waited in line roughly 10 mins, while people crossed to the grove, and people crossed back out from the grove.
The bridge is pretty wobbly, even taking it slow. The wires are good handholds if you aren't steady on your feet. It was a fun walk over to the proper grove.
The grove itself feels like a church of sorts. The crowds that were so chatty in line are all virtually silent at this part, simply taking in the awe inspiring trees. The hollow that the loop follows is also very quiet, so there is a silent grandeur given to the place. This is the section that actually loops(very short) and around each turn is another jaw dropping tree. Pictures really don't capture the sheer size of these trees.
After finishing the loop the wait to cross back over the bridge was shorter. There is river access, a nice sand/rock beach on the loop side, where a few families were cooling off. The river is low, and there are many safe places to swim.
Overall a great trail to see some of Washington's oldest growth trees. Easy, tons of families with small kids on the trail. There were a lot of people but it didn't feel ungodly crowded, especially in the grove itself. If you are in Rainier NP add this one to your list, it will take under an hour and is worth it.

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