A fascinating city to visit – loads to see and experience. Great restaurants, good transport. And unlike most of Australia we experience 4 seasons in the year.
If you are visiting for the anniversary – bring warm clothes. It gets cold at night but days are (normally) almost cloud free. See http://www.holiday-weather.com/canberra/averages/
If you are visiting from overseas or interstate, July is a great time to see the Northern Territory!