This quote by William Dunbar is a tribute to the city of London. It is a celebration of the appeal and magnificence of the city, and a recognition of its value on the planet. The expression "flower of cities all" is a metaphor for London's supremacy over other cities. It suggests that London is the most stunning and desirable of all cities, and that it stands out from the rest. The phrase also implies that London is a source of pride and delight for its people, which it is a location of terrific importance. The quote is a reminder of the city's long and renowned history, and its place in the world. It is a suggestion of the city's charm and its value to the world.