Many displays of the five Olympic rings have been unveiled all over Great Britain in the last few weeks, the most spectacular of them all being the Royal Botanic Gardens, inside London's Kew Gardens. The rings, made up of over 20,000 plants, have a circumference of 15.5 meters each and are visible from the Heathrow flight path. The flowers were planted over a period of five days by a team of volunteers. The flowers used are: Viola “Blue For You”, Viola “Clear Yellow”, Viola “Black Delight”, apple mint and Viola “Red Blotch”. In addition, to celebrate the UK's role in the birth of the modern Olympic Movement, a total of around forty Coubertin Oaks were planted at venues across the whole country. These are trees grown from acorns taken from the English Oak planted in 1890 during the visit of the founder of the modern Olympic Movement, Pierre de Coubertin.