Its exterior was dubbed an eyesore, but the interior of the new Waterfront Hall proved a huge hit yesterday.
While the official opening takes place in May, selected clients were given an opportunity to sample the £29.5m project, work on which should finish this week.
The building, which has already attracted 30 bookings, was last year described as the "sore on the shore", with many complaining that a new extension was not in keeping with the original circular structure or the surrounding area.
Among those at yesterday's event was the Carrickfergus Youth Choir, Irish dancers and drummers, who filled the nine-metre high Hall 1 with noise to show the flexibility of the new space.
Hall 1 is the biggest section at 1,805 square metres. Hall 2 is smaller and more intimate, with windows along one side allowing delegates to see across the city. The building also has meeting rooms upstairs for smaller events.
The extension is kitted out with state-of-the-art technology, providing great sound quality, and the modern fixtures and fittings have been finished to a high standard, adding a sense of luxury.
The impressive venue, which can hold up to 5,000 people, has already attracted big names, including the BBC Good Food Show and the World Credit Union for later this year and the Royal College of Nursing for 2018.
Waterfront sales and marketing manager Suzie McCullough said: "We have 30 events booked in over the next three years, which will generate 70,000 delegates. They booked off-plan, so we're already very excited about this."
The first conference in the new Waterfront, the annual International Surgical Congress of the Association of Surgeons of Great Britain and Ireland will attract 2,000 delegates and bring in around £2.2m.
The Waterfront team is trying to attract more events from outside Northern Ireland, competing with other cities such as Liverpool and Birmingham. And they believe the venue's location will give it an edge. "Most convention centres are similar, but they are not all on the waterfront like this and they don't all have the connectivity with the city centre," explained David Boyce, deputy director for Great Britain at Tourism Ireland.
"We are only 15 minutes from City Airport, and Belfast is compact and easy to get around. Those things put it ahead of other cities."
While the focus is on conferences, Suzie is determined that the Waterfront, which will be able to host three major events at once when finished, will remain one of the most popular entertainment venues in Belfast.
"Our business will grow so much," she said. "We are expecting it to treble, so our entertainment will increase overall. From a local perspective, we want people to understand that it will still be a major entertainment venue."
The project will cost £29.5m, with £11m provided by Belfast City Council, £14.5m by the European Regional Development Fund and £4m by Tourism NI.
Once opened, it is expected to attract 55,000 conference delegates each year and bring in £100m for Belfast by 2020.
Total cost of the extension to the Belfast venue