Tai Tapu Domain war memorial arch.
The following information came from Christchurch City Council:
Large archway and fence made of red volcanic stone including two steel foot gates on either side of archway, forming the vehicle entrance to Tai Tapu Domain. Donated along with the 70-acre domain by Sir Heaton Rhodes in 1921. Six marble plaques are set into the archway in memory of those residents of the area who died during the Boer War and World War I and II.
There is also a DNZB entry on Heaton Rhodes that discusses him donating the land