Several years ago, my wife met me in Santiago for a long weekend while I was working in Sao Paulo.
I must recommend the revolving restaurant downtown. Fabulous veiw, great food at the time. Sorry I can't recall the name.
I visited Vina del Mar with a business associate for lunch and had a lovely time. During this drive we sidetracked to a couple of wineries for some sampling and inexpensive prices on fine wine.
The best adventure was hiring a jeep for +-$75 to venture up to the mineral baths in the andeas. This was arranged through a local tour agency. Ours was a private drive, but there are many tour buses that cover this route. Along the way, we had lunch at a fantastice Swiss chalet with a view that was spectacular.
Sadly, I've not been back. Maybe now that CO is serving the route I'll do it all over again.