Best spots to hike/ visit in the Grampians

My husband and I are going camping in the Grampians over Christmas, for 3 nights. What are some must see and do places/ hikes??

Edit: Thanks everyone, as mentioned, we don't live in Victoria and also naively haven't been keeping up with any news, so hadn't realised the severity of the fires 🔥. Looks like we will have to save the recommended spots for another time! Thank you for the info!