Aside from what's been mentioned, there are great beaches at Camps Bay, Hout Bay and Koggelbaai at the north end of False bay.There's also the Robben Island tour(where Nelson Mandela was imprisoned). Kirstenbach Gardens out near Constantia is also very nice. Believe me, you won't be bored with only 4 days around Cape Town and you'll want to return. The Constantia area has some great restaurants.
