I only visited the Paro Dzong and I found it adequate to get an idea of them. You would have to be blind to miss it: a massive structure not in height a la Manhattan skyscrapers but wide, sloping along the relative large hill and compared to the small modest houses Bhutanese live in it looks like a palace. You can see it from the plane, from the airport, probably from EVERY house in Paro, maybe from space? ;) It is, however, not a palace but the government office.

The first time is on the obligatory tour. I say obligatory but actually you can select the itinerary if you have a private tour and this is just one of the must-do things in town and it is totally worth it. The dzong is still in use by the government, or religious government, and you cannot visit anything but the entrance hall and courtyard plus one of the temples. If you think stepping through the gates is already impressive just wait for the view from the terrace. Of course the guides can tell you everything you want to know. Try asking something about the place you think they wouldn't know after the hundredth or thousandth tour they have done - they will maybe not be able to tell you due to the language barrier but not because they don't know. I also loved that the driver drops you at the top of the hill's parking lot and you can descend to the lower area where the river (cleanest river ever?) flows. Later in the evening I got a lovely view of the lit dzong when returning from the local family visit.

I think this should be the 3rd place on the WHS after Tiger's Nest + Manas. It's unclear what has taken Bhutan so long after finally joining the convention and submitting everything in one swoop in 2008 only to leave it dormant for over 10 years already.