The good parts of Wild Basin are really good, but they're a long way from the trailhead. This is a link-up of the two northernmost portions of the basin up and over Mt. Alice and Boulder Grand Pass on the Continental Divide. As written here, the loop is 9 miles, but you've got at least four miles each way in addition, making this a big, challenging day in the mountains.
This is definitely not a beginner route and you should be comfortable with exposed scrambling, steep talus, and loose scree descending. Once you're committed to the Hourglass climb, there is no shelter, so check weather and personal conditions carefully before committing. In the early season, snow can fill Boulder Grand Pass making it ... not a run. Be prepared to turn back to the Lion Lakes (still a mighty destination) if conditions look anything but ideal.
To get to the start of this route from the Wild Basin trailhead, you'll need to run either the Ouzel Lake Trail
or the more direct but less interesting North St. Vrain Fire Trail
. Either one is about 5 miles. Start at the split between the popular Thunder Lake Trail
and much less travelled Lion Lake Trail
The run up toward Lion Lakes is steep and rough, but the payoff is worth it! The lower of the two Lion Lakes is especially spectacular with a stunning view of a big pointy mountain. That's Mt. Alice! Skirt the lake on the north side and follow a faint trail upwards. If you can't find the trail, just follow the path of least resistance. Pass the upper lakes on the south side (by the time you see them, you'll be above them), aiming for a broad ramp leading to the Divide just north (right) of Mt. Alice. It's steep, but every step makes the view better.
From the saddle on the Divide, the going gets serious. Here is a good place for a frank assessment of conditions. Once you're on the Hourglass, you're committed to two miles of high-exposure (though not difficult) terrain to the summit and then down to Boulder Grand Pass. There is no shelter from bad weather and there's no shame in retreating to the Lion Lakes from here.
If all systems are 'go,' turn left and notice the huge Hourglass Ridge (north) face of Mt. Alice. The whole thing is an unrelenting steep slope of large talus, but the crux lies at the very bottom where the ridge narrows to a knife edge. Find your way through this carefully. You'll probably need to drop significantly to the left (east) side of the ridge in at least one spot before attaining a small saddle at the base of the main face. Once on the face, there is no trail; just pick the most logical-looking route and start clambering.
Once you get to the summit (don't worry, you'll know when you get there!), the hardest part is over. Take a moment to enjoy the STUNNING view of Longs Peak, Chiefshead, Taylor, Isolation, and all the other local 13,000-foot peaks. This is truly a magical spot!
To continue, pick your way south off the summit, aiming for the broad tundra slope obvious below. Again, there is no trail, but follow the path of least resistance. After about a mile and 900 feet of descent, look for the lowest point on the eastern edge of the plateau. This is the top of Boulder Grand Pass and you'll see Lake of Many Winds below you. (Watch the cool pattern of winds ruffling its surface and you'll understand the name.) Boulder Grand Pass isn't much fun, but the best route is hard up against the left (northern) wall of the scree slope.
Once down at Lake of Many Winds, give yourself a pat on the back for safely making it over Mt. Alice. Traverse around the north shore to find a faint trail. The trail is steep but exceedingly scenic and becomes more obvious the farther you go. You'll drop down several steep pitches alternating with flat, flower-strewn meadows with waterfalls. Several rock ledges will interrupt your flow. Back down in the trees, you'll find a series of log bridges leading through the marshy area at the head of Thunder Lake.
From Thunder Lake, the trail is obvious. Two miles on the well-worn Thunder Lake Trail
brings you back to the start again. Well done! Soak your feet in the creek at the trailhead and have some snacks; you've earned it for sure!