For today's Geo Quiz, we're following a river that runs through Bangkok.

River of kings: photo: Heinrich Damm

It's the site of this week's celebrations of the birthday of Thailand's King Bhumibol Adulyadej.

The world's longest serving monarch turns 80 tomorrow.

There will be golden float processions on the river and fireworks displays in the night sky.

The dominant color in Bangkok this week is....PINK.

Pink Polo shirts are flying off the shelves of Bangkok's Phu Fa Fashion shop:

“Yes, yes has been very popular, it' s almost 100,000 pink polo shirts that we sell as a matter of fact the whole collection is 7 colors but the most popular color is pink.”

We'll tell you why Bangkok is awash in pink. But first, see if you can come up with the name of Thailand's principal river. One more hint...its name means "river of kings."

We'll have the answer here...