An Ant Nest On The Ceiling??

Last week, I went to school as usual. When it was finally the last subject that I need to attend, I felt so relieved because I get to go to the computer lab for the subject. The computer lab is equipped with air-conditioners which is quite a relaxing place to study. As I went up to the lab, I saw something that gave me a shock! At first, I thought it was a beehive or something but it wasn't. I just happened to look at it closely as I was accidentally being pushed by a friend. I saw many big, black ants bringing some soil up to the ceiling to make a nest. It was quite amusing. I was thinking maybe, we, the humans always destroy their nest which they made on the ground. Therefore, they have no choice but to build their nest at a higher place. This is actually my first time seeing this! I should have took a picture of it, but I do not have a camera...T_T. Anyway, I think the ants looks like this: