The Dimmsdale Observatory is a scientific building in Dimmsdale used to observe objects in space.
The Observatory played a minor role in the episode, "Pipe Down!", when a scientist working inside spotted a large meteor heading straight toward Dimmsdale. As a wish by Timmy muted all forms of sound, the scientist had to run out of the observatory and bring Chet Ubetcha to the observatory to see the meteor himself. Chet panicked, spitted out coffee, and sounded an (now silent) alarm on his news cast, and then fled to the Mexican border as the meteor started to approach the city. Cosmo and Wanda were watching this and went to warn Timmy of this. Thanks to some charades, Timmy was able to get all the sound back to the world as well as get rid of the meteor before it destroyed Dimmsdale.
It is a dome shaped building with a large telescope sticking out of an opening in the dome. Inside is the eye piece of the dome, and several panels for electronic equipment.