You can opt either for Park Plaza or Taj - these are the best 5 Star hotels in Chandigarh.
Apart from these, Lemon Tree, Icon Boutique are also good.
Rock Garden, Sukhna Lake, Rose Garden, Iskon, Fun city, Leisure Valley are nice places to see. Since it is a modern city, you will not find much historical or traditional places. Chandi Temple is only one I know.
If you are a foodie, you are going to love chandigarh. Makke di roti with sarson da saag is one of the most famous cuisine. Punjabi Cholle with Amritsari Naan are also famous. If you are Non Veggie, you should definately try Butter Chicken and Amritsari Fish. Brabeque Nation, Chawla's, Sagar Ratna and Sher-e-punjab are some of the best restaurents to try.
Thanks,
Shashank