Excepting the shoreline of the Firth of Forth, Edinburgh is encircled by a green belt, designated in 1957, which stretches from Dalmeny in the west to Prestongrange in the east. With an average width of the principal objectives of the green belt were to contain the outward expansion of the city and to prevent the agglomeration of urban areas. Expansion affecting the green belt is strictly controlled but developments such as Edinburgh Airport and the Royal Highland Showground at Ingliston lie within the zone. Similarly, suburbs such as Juniper Green and Balerno are situated on green belt land. One feature of the Edinburgh green belt is the inclusion of parcels of land within the city which are designated green belt, even though they do not connect with the peripheral ring. Examples of these independent wedges of green belt include Holyrood Park and Corstorphine Hill.