The 44th Belfast City Marathon is being held on Sunday, bringing thousands of participants and spectators onto the city's streets.
The 26.2 mile route will take participants across the city, starting in east Belfast before finishing in Ormeau Park in the south of the city and taking in the north and west along the way.
As a result many roads will be closed for much of Sunday and public transport will also be affected.
The first Belfast City Marathon was held on the same date in 1982, with more than 3,000 participants starting at the former Maysfield Leisure Centre near the city centre.
The race gets under way at the Stormont estate in east Belfast.
The wheelchair race starts at 08:59 BST, the elite race starts a minute later and all other participants at 09:01.
Participants start on Prince of Wales Avenue, and proceed down the hill, on to the Upper Newtownards Road.
Abay Alemu, an international elite runner from Ethiopia, has a personal best time of 2.06.50, so the first runners are expected to cross the finish line shortly after 11:00 BST.
But the rest of the runners will still be making their way across the city for a number of hours after that.
Roads will reopen after six hours, so everyone continuing along the route after this has been asked by the organisers to join the footpath and adhere to road safety laws.
Just under 24,000 people have signed up for the marathon.
However, organisers say there is usually a 10-15 % drop off on the day of the event.
Marathon entrants must be over 18 years of age and team relay entrants must be over 16.
While it is obviously hard to predict just how many people will come out to watch, it is estimated there will be anywhere between 70,000 and 100,000 spectators.
To help people going to the marathon there will be special early morning trains from Londonderry, Larne, Bangor, and Newry to Belfast Lanyon Place.
For a list of all special departure times click here.
These additional services cannot be booked in advance and standard fares will apply.
Public transport around the city will be affected due to several road closures.
Ulsterbus, Metro and Glider bus services within Belfast will be subject to delay or disruption.
Shuttle buses will be available from Belfast City Hall and Lanyon Place Station to the starting line from 07:00 BST and 07:30 BST respectively.