Among colleges, my alma mater, Agnes Scott, is exceedingly lovely in a very structured, pruned way. For the wilder look, Mount Holyoke is very beautiful.
Yeah, Pepperdine’s a good one. Here’s one of the official pictures of the campus, for those who aren’t familiar with it, and here are some I have taken. Not much in the way of classical architecture or anything, though.
Another one is the U.S. Air Force Academy.
Another vote for University of Chicago. Absolutely gorgeous (though not so much if you wander a few blocks off campus).
Iowa State, other than the parking-garage-school-of-architecture and new our-department-has-more-money-than-yours-EVER-will engineering buildings - lovely quad, huge campanile, lake with gay swans*, old brick buildings, ivy.
*After a long struggle with swans - a pair of trumpeters in 96 that roamed freely and could often be seen trying to tear the mudflaps from an unfortunate car, another pair that were penned up in the lake, the school finally got two mute brothers in 2000. Someone (of course) had to write in saying that having two male swans (instead of the traditional male and female, traditionally named Lancelot and Elaine, which always pissed me off, given that Lancelot didn’t love Elaine, but I digress) would promote homosexuality and give the impression that the school approved of/ encouraged homosexuality.
UC Berkeley is woodsy and quite scenic … views across the bay and out the golden gate, redwood groves on campus, classic architecture, lots of open space back in the hills.
15 miles south is probably the ugliest campus I’ve ever spent time on, Cal State Hayward.
I feel that everywhere I’ve been educated has been fairly attractive aesthetically.
The U.S. Military Academy at West Point has so much history to it, it was quite interesting to someone who is a big history buff like myself.
Lots of the buildings are from the era of men like Lee and Grant, and it’s awe-inspiring to think you were walking in their footsteps.
UVA was also very aesthetically pleasing in a different way, as others have already mentioned.
As a University of Michigan guy it pains me to give props to a pac-10 school but…
Stanford is the best once you take weather, architecture, landscaping, and general collness of feeling into account.
We got some of those here at the Univ of South Florida, which will win no design awards ever.
Our SunDome, our Rec Center, and a mighty fortress is our library. The old parts of campus have a serious post-Stalinist Soviet apartment bloc feel, and the new parts are the terribly clichéd late-'90s red brick numbers with green roofs. The other campuses of this university are no better.
I don’t think U of Florida is much better, it’s very compact, but very blah.
The only problem I have with Stanford is all the cracks in the walls. They must have some earth shaking events happening there. 
University of Cape Town is pretty ho-hum, but the setting halfway up the slope of Devil’s Peak is quite unique.
I also liked both Oxford and Cambridge…
but absolutely the most impressive campus I’ve seen myself is the University of Venice, spread out over such pallazos as Ca’Foscari and Ca’Dolfin
Some of the Oxford colleges have beautiful buildings and grounds. And some of the University buildings (such as the Exam Schools and the Ashmolean) are impressive. But its not a campus university so can it really count as one of the most aesthetically pleasing university campus?
Another vote for Duke, which has a west campus of gothic architecture (patterned after Princeton) and an east campus of Georgian architecture. Both very attractive.
And for scenic beauty, I’ll put in a vote for tiny Covenant College, which sits astride Lookout Mountain and has a panoramic view from both sides. A stately former resort hotel is the centerpiece of the campus.
But I am surprised no one has mentioned Cornell University.
The gorges are the single most stunning natural feature I have ever seen - and I got to live 20 feet from one for two years, lucky me.
Some of the buildings are not the best (Uris Library, aka ‘Rustbucket’), but the grounds (hundreds of acres of woods &c) and many of the older buildings are lovely (and now, all heated!).
I second the vote for Northwestern (tho’ I am biased, having grown up 3 blocks from campus) and also Stanford.
Here in Oxford, I think it really depends on the college. Some are beautiful (like mine!) and some are garish, and some are 60’s-functional.
Daphne
Stanford University is my choice for beautiful campus. I cannot argue with the other choices however
The first campus that came to my mind on reading this thread was Stanford. I also enjoyed the appearance of Oxford.
Ohio State was a very nice campus. For me to poop on.
Links, people, links. Here’s Cornell.
Linfield College in McMinnville, Oregon.
I didn’t go there, but I wandered around when I was in HS. It looks like a college should look, when you’re imagining a college. It’s gorgeous and college-y.
And Stanford is lovely.
The year I was at Mount Holyoke College one of the ratings-type magazines labeled it the Most Beautiful Campus (as well as one of the top ten non-party schools but that’s neither here nor there) so my vote would be for MHC.