the thickest fog i've ever experienced has been in dubai - in 2001 i was staying in one of the jumairah beach hotels, first time there, it wasn't so built up back then, around dawn i saw the really dense fog and walked out onto the beach to see what it was like
of course i got lost! couldn't see the hotel, nothing but sand and fog in all directions, luckily i realised i could retrace my steps in the sand
the best foggy morning there was a couple of years ago, i'd checked in early to get a points upgrade to UC, then just after boarding a delay was announced due to the fog, so i enjoyed an extra couple of hours swigging bubbly before takeoff