The foundation was first laid at a ceremony in St John Street on a rainy April morning in 1864.

Tasmanian governor Thomas Gore Browne told the assembled crowd that the hall would be a "handsome building" which would add to the city's beauty.

The town hall was completed in 1897, and underwent a major extension in 1936 when the original four Corinthian columns were extended by five.

Launceston architecture and Lego enthusiast Ken Draeger was last year able to combine two loves when he started a 12-square-metre scale model of the Civic Square precinct, which includes a very specific representation of town hall.

Mr Draeger said the project started with the town's post office and clock tower, and spread to include the Johnstone and Wilmot building, the Telstra exchange, Henty House, the Magistrates Court, among others.

The entire project, based on photographs and Google Earth, has used 250,000 individual Lego bricks, and cost Mr Draeger an estimated $35,000.

It has taken more than a year to complete.

Launceston Mayor Albert van Zetten said he was amazed by the town hall's immaculate condition and bold presence when he first started as a city alderman in 2005.

"It is an incredible building for Launceston and something we can be proud of," he said.

The iconic building will be celebrated in a special ceremony to be held within its walls on Tuesday, April 15.

An exhibition that details its history will be open to the public the following day.

Mr Draeger's representation of the Civic Square precinct will be on display at this year's Brixhibition charity event at Kings Meadows High School on April 26 and 27.