This was postmarked in Christchurch and the postmark has an image of the Christchurch Cathedral on it. Despite surviving several earthquakes in the past, the last big one to hit Christchurch in 2011 seriously damaged the cathedral and the decision was made to demolish the entire structure and build a new one.
The stamp on this cover is a round kiwi definitive. New Zealand Post has been producing this for a number of years now. Different colours and denominations are used every year.