Bhutan has some of the emptiest trekking in the Himalaya, for a simple reason: every trekker travels with a licensed guide and a support crew, and the daily fee applies throughout. The result is trails where you may meet nobody for days.
Druk Path — five or six days
The Druk Path links Paro to Thimphu over a ridge, reaching about 4,200 metres. It passes high lakes stocked with trout, the ruined Jele Dzong, and rhododendron forest that flowers spectacularly in spring. It is the standard introduction: short enough for a normal itinerary, high enough to be a real mountain walk. Most people manage it with ordinary fitness, provided they have acclimatised first.
Jomolhari — seven to nine days
The Jomolhari trek climbs from the Paro valley to Jangothang base camp beneath Jomolhari (7,326 m), one of the great faces of the Himalaya, and crosses passes above 4,900 metres. It goes through yak-herding country and the settlement of Lingzhi, and it is the classic Bhutanese trek — considerably harder than Druk Path, with real altitude and cold nights under canvas.
The Snowman Trek
The Snowman Trek is regularly described as one of the most difficult treks in the world. It runs roughly 25 to 30 days across the far north, crossing eleven passes above 4,500 metres, several over 5,000, through the remote Lunana region. Fewer than half of those who start it finish; the weather closes passes without warning and there is no easy way out once you are committed. It runs only in a narrow window in autumn, and it requires genuine high-altitude experience.
Season
The trekking seasons are spring (March to May) and autumn (late September to November). Autumn gives the most stable weather and the clearest mountain views; spring brings rhododendron and magnolia in flower but hazier air. The summer monsoon makes trails wet, leech-ridden and the views non-existent. Winter closes the high passes.
Practical matters
Camping is the norm — there are no teahouse networks as in Nepal. Your crew carries tents, cooks, and moves loads by pony or yak, which is why the logistics are arranged entirely through your operator. This also means the trek is not cheap: the daily Sustainable Development Fee applies on trek days as on any other.
Altitude is the main risk, and evacuation from the remote routes is slow and expensive. Insurance covering helicopter rescue is essential. Bring a sleeping bag rated well below what you expect to need — nights above 4,000 metres drop hard even in October.
One point of etiquette: Bhutan does not permit mountaineering. Peaks above 6,000 metres have been closed since 2003 because they are regarded as the homes of protected deities. Gangkhar Puensum, at 7,570 metres, remains the highest unclimbed mountain in the world for this reason.