Cave Rock / Tuawera is a rock formation on Sumner Beach, reached from the Esplanade in Sumner, Christchurch, rated 4.6 on Google from 1209 reviews. It has a walkable cave, views along the beach and a rich Māori history. The website link goes to the Christchurch City Council's general site, which says nothing specific about the rock.
A natural landmark like this is best visited with the tide and weather in mind. Check the tide times before you go, since waves can reach the base of a rock on a beach at high tide, and wear shoes that cope with wet sand and rock. Take care on slippery surfaces and keep children close to you. Landmarks with Māori names carry cultural meaning, so look for signs that explain their history and treat the site with respect. Early morning or late afternoon light suits photographs, and a walk along the beach afterwards rounds off the visit.
For a short coastal stop and some local history in Sumner, Cave Rock is a well-liked place to visit.