Santiago is a city that is close to many diverse activities from the Andes mountains, to the beaches less than 2 hours away to white water rafting and kayaking in the (very cold) Maipo river shooting rapids while surrounded by the Andes Mountains and home to many wonderful vineyards. A very special place to go to in the Maipo Valley is Lodge Andino (see my review on that). Don't forget to visit Valparaiso and Vina Del Mar and surrounding area. The food is great no matter where you go, from Empanadas (including shrimp filled) to the (minimum) 4 course dinners which are plentiful. Wines are great, fruits delicious and the hospitality is terrific. Chile is a tourist friendly country, unlike some others, especially in Europe. Be ready to slow down and take your time no matter what you are doing. No one is in a hurry in this lovely country. Make sure you know the important phrases and if you do not know spanish, begin with "no habla espanol, habla _____"<-fill in the blank out of courtesy to the Chileans, This small courtesy will get you very far instead of just saying Habla _____<---your language. The public transportation system is great and if you are staying beyond a couple days, buy a transportation card which gives you access to the very clean subways and buses.
I will definitely go back there and include another much longer stay at Lodge Andino and more time at the beach as well.