The event, which marked the end of the New Zealand International Science Festival and the beginning of the Cadbury Chocolate Carnival, in collaboration with the Dunedin City Council, attracted about 2500 people.
Science interest talks, live music, chocolate demonstrations, and bouncy castles were all a hit with the crowd.
US science rapper Tom McFadden helped judge the Science Idol final in which children who took part in science rap workshops last week shared their songs with the public.
Mr McFadden said the workshops were "awesome" and he enjoyed working with them to create "impressive" raps.
Kate Truman and Helen Knott won the 8- to 10-year-old category with their duo about chemistry, and Ella Cameron won the 11- to 13-year-old category with her rap about fireflies.
They each won a map of their DNA, thanks to Genetics Otago and the Otago Institute.
The winner of the dessert competition was also announced.
Greg Piner, Pier 24 chef, said the standard in the competition, which attracted nine entries, was "very high", making it difficult to choose a winner.
First place went to James Musk, of Ironic Cafe and Bar, followed by Brett Cafun, of Scenic Hotel, and Im Konsila, of Mercure Hotel.
Mr Musk said "lots of practice and trying the flavours together" enabled him to create the winning dish, dubbed the "Tantalising Teaser".
Science Festival director Sue Clarke said the festival's more than 200 events opened the world of science to everyone.
Many of the workshops were booked out well in advance and the `science of' events including beer, curry, seafood and wine had been extremely popular, she said.
The chocolate carnival runs until July 17.
