A 1.9-mile off-trail segment connects Thunder Lake, Snowbank Lake and the Lion Lakes in Rocky Mountain National Park. The clockwise route follows a well-maintained trail to Thunder Lake, then veers north on a steep off-trail climb that levels across stunning alpine flats between drainages.

The off-trail portion of the route crosses high, open alpine flats between the Thunder Lake and Lion Lakes basins

A steep, 660' climb from Thunder Lake levels off near this tarn, whose outlet forms Fan Falls below

The route scales a very steep ridge with excellent views over Thunder Lake

Maintained travel resumes on the grassy northeast shore of Lion Lake #1

A well-formed social trail connects Snowbank Lake with the maintained trail at Lion Lake

Crystal clear tarns dot the broad expanse between drainages

The maintained trail leads to the Thunder Lake inlet area (pictured here), where you'll veer north to begin the steep climb toward Lion Lake

If pressed for time, it's easy to skip Snowbank Lake and continue on a relatively flat line to Lion Lake #1 (pictured here)

You'll have a good view of Boulder Grand Pass (12,061') from high points over Thunder Lake, and the challenging couloir that must be scaled to reach it

While the lakes are worthy destinations by themselves, open, relatively easy alpine travel between them is the route's true highlight

There are no designated backcountry campsites at Lion Lake #1, though limited zone camping permits are available

Snowbank Lake sits under Chiefs Head Peak (13,579') along the Continental Divide

Trio Falls drops between Lion Lake #2 and Lion Lake #1

Hikers can minimize impact on sensitive alpine vegetation by walking on rock slabs and in single file whenever possible

Thunder Lake (10,574') sees heavy traffic throughout the summer and early fall, but few continue beyond it to Boulder Grand Pass, Falcon Lake or over to the Lion Lakes

Hikers must cross Lion Lake's rushing inlet to pick up the maintained trail on the far side

Lion Lake is distinguished by flat, grassy meadows around much of the shore

I hiker stands over a tarn on the cross-country section between drainages