<P> The course begins at three separate points: the' red start' in southern Greenwich Park on Charlton Way, the' green start' in St John's Park, and the' blue start' on Shooter's Hill Road . From these points around Blackheath at 35 m (115 ft) above sea level, south of the River Thames, the route heads east through Charlton . The three courses converge after 4.5 km (2.8 miles) in Woolwich, close to the Royal Artillery Barracks . </P> <P> As the runners reach the 10 km mark (6.2 - mile), they pass by the Old Royal Naval College and head towards Cutty Sark drydocked in Greenwich . Heading next into Deptford and Surrey Quays / Rotherhithe in the Docklands, and out towards Bermondsey, competitors race along Jamaica Road before reaching the half - way point as they cross Tower Bridge . Running east again along The Highway through Wapping, competitors head up towards Limehouse and into Mudchute in the Isle of Dogs via Westferry Road, before heading into Canary Wharf . </P> <P> As the route leads away from Canary Wharf into Poplar, competitors run west down Poplar High Street back towards Limehouse and on through Commercial Road . They then move back onto The Highway, onto Lower and Upper Thames Streets . Heading into the final leg of the race, competitors pass The Tower of London on Tower Hill . In the penultimate mile along The Embankment, the London Eye comes into view, before the athletes turn right into Birdcage Walk to complete the final 352 m (385 yards), catching the sights of Big Ben and Buckingham Palace, and finishing in The Mall alongside St. James's Palace . This final section of the route formed part of the 2012 Olympic Marathon Course . </P> <P> Since the first marathon, the course has undergone very few route changes . In the first race, the course took a diversion around Southwark Park before re-joining Jamaica Road on the way to Tower Bridge and was routed through St Katherine Docks past the Tower Hotel, en route to the Tower of London and the cobblestoned stretch of road that in later years was carpeted, to help runners prevent injury on the uneven surface . In 1982, the finishing post was moved from Constitution Hill to Westminster Bridge due to construction works . It remained there for twelve years before moving to its present location at The Mall . In 2005, the route around the Isle of Dogs between 22 and 34 kilometres (14 and 21 mi) was switched from a clockwise to an anti-clockwise direction, and at 35 km (22 miles) the route was diverted to avoid St Katherine Docks and the cobblestoned area near the Tower of London . In 2008, a suspected gas leak at a pub in Wapping diverted the course, but in 2009 the race followed the same path as in 2007 . </P>

Where does the london marathon start and end