There is essentially one road through Bhutan, which follows a series of mountains and valleys. Most travelers will follow this road from east to west, starting from Paro (the home of the country’s main international airport). How far along the way you travel, and how many mountains and valleys you visit will depend on the length of your trip or your preferred pace of travel.
Each valley has its distinct character, and most have excellent accommodation options. Paro, Thimphu, Punakha & Gangtey are most widely visited, and would most likely be considered the ‘core’ areas in a Bhutan holiday. To get further off-the-beaten-track, visit Bumthang (the far eastern, agriculturally productive valley from which you can fly one way back to Paro) or Haa, which is just one valley to the east of Paro but scarcely visited.
With its Himalayan terrain, Bhutan makes a brilliant destination for trekking. The country offers treks for all levels, from meandering walks to intensive challenges; tell your consultant your preferred level, and they will be happy to tailor your excursions to suit.
Bhutan can also work in combination with other Asian destinations. There are connections with India (should you want to contrast the pace of India with the zen of Bhutan!). You could hop to Thailand too, or even combine with The Maldives (if a beach stay is a high priority).
But Bhutan is a journey in itself that has to be experienced to be believed.