Halong Bay, with its karst limestone formations jutting out of the water, is similar to Guilin, China. Unfortunately, I went on a rainy, overcast day.
I joined a day tour from Hanoi to Halong Bay. This was quite rushed, as I only got to spend 4 hours on a boat cruising the bay. Of this, about 2 hours were spent eating lunch (boat stationary) and waiting for the other people to kayak. The highlight was definitely admiring the dramatic scenery, quite appropriate for a painting or movie. I also enjoyed the one cave we toured. Inside, there were large stalagmites and stalactites and limestone shaped like creatures.
Lastly, my camera lens broke the day before, so this is the first place where I do not have pictures for. However, I will most likely purchase another one when I get back to Hanoi.