Pity you missed the busker festival in ChCh. It was mucho fun!  The city walks are good & free! , sights include  monument to the womens movement, NZ was first country where women got the vote,  and  Rutherfords Den is interesting if you are into science. (he split the atom). I also like the Huge oak tree, grown from aa Acorn sent back by a soldier during WW I, he died, but his tree still grows on the banks of Avon river, ChCh, NZ.
Takes a couple of hours + stops along the way. 

Pity CHCH  police station is so ulgy!!