The golf ball.
26.5 foot diameter microwave radar dome for the earth and planetary science department. Rumor has it that it does wonders on microwave lasagne (but it
won't defrost.)
Hacks
In 1983, it was covered with a yellow tarp painted to look like a large smiley face. Then, in 1986, it was decorated again: this time to look like the crown of the Statue of Liberty for the fourth of July.