The screen, which went up last month, will be showcasing a number of sports events in the run up to the London 212 Olympics.
"There will be a real party atmosphere with a picnic area on the east lawn and food traders offering a selection of choices," said Belfast Mayor Niall O'Donnghaile.
No tickets are required for Sunday's screening and entry is free.
COMMENT RULES: Comments that are judged to be defamatory, abusive or in bad taste are not acceptable and contributors who consistently fall below certain criteria will be permanently blacklisted. The moderator will not enter into debate with individual contributors and the moderator’s decision is final. It is Belfast Telegraph policy to close comments on court cases, tribunals and active legal investigations. We may also close comments on articles which are being targeted for abuse. Problems with commenting? firstname.lastname@example.org