Small Sistema container under a rock on the way to Mueller Hut at elevation 1600m.
Mueller Hut Route is quite a demanding hike with unforgiving 2200 steps leading you to Sealy Tarns, and from there a more rugged way, zig-zagging up the tussock slope that gradually becomes more rocky, turning into a boulder field. Cache is hidden just meters off the route marked with orange poles. It provides you with an excuse to take a break and admire the views. It takes roughly 3 hours to reach the cache from White Horse Hill campground. 4 hours to reach Mueller Hut.
There's a story about the cache name - we had just hidden it and were trying to think of a good cache name. We wanted to draw some parallels with any Star Wars location because we had this R2D2 trackable on our hands that wanted to travel to SW themed caches. And as we couldn't find any already there we though we'll hide one ourselves! While we were struggling to find a name for the cache, two girls that were passing us by excitedly announced: "Did you notice the Face in Mount Cook!? We saw it and we thought we need to tell everyone!"
Indeed, without even the need for them to point at anything, we looked up at the south face of Mount Cook and saw... the face of Aoraki? So, it was clear now - Star Wars can wait, we now knew the title of this cache!
We thought it may be something of temporary nature but turns out it's not new - there's a Stuff article about this 9 years ago already.
Mueller Hut Route is rated as Advanced: Tramping Track by DOC yet it is still highly popular and could be done by anyone of average fitness level in summer months. In fact, it is so popular that you will probably need to exercise stealth in order to retrieve the cache.
Still, be prepared for sudden weather changes and pack extra layers of clothing, even in the middle of summer. Always check the route and weather conditions before you go at the Mount Cook Village visitors centre. Mountaineering skills, avalanche recognition and snow/ice gear required in winter (June-August)!
See DOC website for more information.