The Blackcaps have built a commanding lead on a dominant day two performance against Bangladesh.
New Zealand reached 451/4 at stumps - 217 runs ahead of the tourists, who toiled hard without much reward on a placid pitch.
The plaudits will be reserved for Jeet Raval (133) and Tom Latham (161) who put on 251 for the first wicket - a record opening stand for New Zealand against Bangladesh.
Chasing 234, the home side resumed at 86/0, with the pair continuing through to a century stand and shortly afterwards celebrating their record partnership with Raval reaching his first test century in the process.
Raval reached his milestone off 163 balls shortly before lunch.
Since debuting for his country in 2016, the Auckland batsman had achieved seven fifties across 16 tests, without ever converting them into centuries.
His previous best score was 88.
But he put that in the past at Seddon Park, striking 19 boundaries and a six in a chanceless innings.
He was eventually dismissed after lunch for 132 from 220 balls.
Bangladesh captain Mahmudullah brought himself on for an over and was rewarded when Raval played across the line to a straight delivery and got a leading edge to Khaled Ahmed at mid-off.
Latham was joined by Williamson and passed 150 for the fourth time in his career. Their partnership was broken at 79 though when the Cantabrian was caught at third-man off the bowling of the part-timer Soumya Sarkar.
Ross Taylor came and went quickly – trapped lbw by Sarkar for four runs before a confident Henry Nicholls joined Williamson.
The pair put on a brisk century stand with Nicholls (53) looking sublime before he missed a straight one from Mehidy Miraz with just two overs left in the day.
All the while Williamson continued to collect runs and will start day three just seven further runs from a 20th test match century.
Neil Wagner's sixth test five-wicket bag helped the Blackcaps overcome a great start by Bangladesh on day one.
Opener Tamim Iqbal scored 126 and his team were 121/1, before the NZ bowlers found their line. Bangladesh lost their last five wickets for 27 runs, with left-armer Wagner taking 5/47.