Seven-year-old Pearl Richardson from Newcastle told Premier she was "so proud" to put the finishing touch to the structure which consisted of 300,000 bricks and took three years to plan and build.
The model - which is 3.84m long, 1.53m wide and 1.7m high - forms part of an international fundraising effort for an exhibition centre at Durham Cathedral.
Open Treasure allows visitors access to previously restricted areas of the cathedral and the opportunity to showcase the landmark's artefacts.
Premier's @ianbritton reports on the largest ever #LEGO #model of @durhamcathedral for #InspirationalBreakfast! pic.twitter.com/seKIeaO8jI
— Premier Christian (@PremierRadio) July 26, 2016
The Very Reverend Andrew Tremlett, Dean of Durham, told Premier: "It is astonishing. There is a map right next to the cathedral which shows the 195 countries of the world and I think 182 of them have a pin in them which says that people have come and donated from that country.
"As well as being a great fundraising opportunity, this is also a way to help people connect with the cathedral. This is a very fun way. It's great to see the young and old engaging."
Durham Cathedral's Head of Development, Gaye Kirby, said: "We've been overwhelmed by the generosity of our visitors and it has been wonderful to watch the model taking shape."
You can listen to a special report by Premier's Northern Correspondent Ian Britton by clicking here.