On the outskirts there is a hot chalybeate spring.
The fields and places of entertainment in Islington were favourite places of resort for the citizens of London in the 17th century and later; the modern Ball's Pond Road recalls the sport of duck-hunting practised here and on other ponds in the parish, and the popularity of the place was increased by the discovery of chalybeate wells.
The first is a watering-place (pop. 2074), with pleasant sands and a chalybeate spa; the second (pop. 3086) has iron foundries, engineering works and fish-curing establishments.
The island is watered by several short rivers, mainly on the east and south; there are numerous fresh water springs, as well as hot chalybeate and sulphurous springs.
Large quantities of mineral water, sulphur, chalybeate and lithia, bottled at Meridian, Raymond and elsewhere, are sold annually.
In the Frederiks Park is a pump-room supplied with a powerful chalybeate water from a spring, the Wilhelminabron, in the Haarlemmer Polder not far distant, and in connexion with this there is an orthopaedic institution adjoining.
There are three parks, one of which, Lake Park, is a pleasure and health resort, with a lake and chalybeate and sulphur springs.
It was formerly famed for the chalybeate springs to which it owes its name, and in 1621 was visited by Charles I.
The place is chiefly noted for its sulphur and chalybeate springs, the former being the strongest of the kind in Wales.
A good road runs southward down the pass, passing after a few miles some large chalybeate and sulphur springs.