After a bit more than a 16+ hour van and bus ride from Pasto, Colombia, the Tatacoa did not disappoint. I stayed in the nearby town of Aipe which is on the other side of the Magdalena river which we crossed in steel shallow bottomed boat to the Villevieja side. It was so hot with nearly no air movement, but once inside the 'desert area', it was miraculously much cooler - clouds where granting us some much appreciated shade as well.
According to this, UNESCO article on the Tatacoa desert, it turns out that it's not classified as a desert, but rather "a dry forest tropical ecosystem".