This circuit takes you from the plains straight into Sikkim's high snow country, with Lachen as your base for a run at Kala Patthar and the wide meadows of Yumthang Valley. It's a Protected Area route, so the permit is handled for you, and the pace is built around one long high-altitude day bookended by easier travel days through Gangtok. Expect river roads, waterfall halts, a village homestay night, and mountain views that only open up this far north.