Bhutan charges a daily Sustainable Development Fee and requires every visitor to travel with a licensed operator. The effect is a country that has stayed remarkably intact, and a trip that is worth planning properly.
Most itineraries run Paro to Thimphu to Punakha and back. We would add the Phobjikha valley, where the black-necked cranes winter and the nights are properly cold, and give you a day’s walking between villages rather than another dzong.