are a number of lakes and reservoirs. The rocks are also rich in minerals and there are many abandoned mine sites where copper, lead and silver have been mined since Roman times. The river valley downstream of Betws-y-Coed is relatively wide and fertile, and supports dairying and sheep rearing. In the winter, these pastures are used to nurture the sheep brought down from the mountains to avoid the worst of the winter weather. SSSI Aber Afon Conwy is a site of special interest. It has acquired such a status due to its marine and terrestrial biology. The tidal reach of the site is around . Its upstream boundary is south of Tal y Cafn, and the whole site encompasses Conwy Bay. The shoreline is supported by natural rock, in addition to boulder clay cliff, sand dune, salt marsh and woodland. Culture and history The scattered communities along the Conwy valley have ancient traditions with archeological evidence of habitation back to the Stone Age. The Romans occupied this area up to 400 AD and there has been continuous habitation since that time. The valley is home to two of the oldest churches in Wales, those at Llanrhychwyn and Llangelynin, which respectively date back to the 11th and 12th centuries. Much of the Conwy valley was laid waste in the Wars of the Roses by the Earl of Pembroke, under the orders of Edward IV, the Yorkist king, following a Lancastrian attack on the town of Denbigh in 1466. At the mouth of the Conwy as it discharges into Conwy Bay is the town of Conwy with its World Heritage Site castle — Conwy Castle and two famous bridges. One of the earliest suspension bridges by Thomas Telford now carries a footpath whilst Robert Stephenson's tubular iron bridge still carries the main Holyhead to London railway line. A third bridge now takes road traffic, and more recently still the A55 now runs in a tunnel under the estuary. Water quality Neither the River Conwy or its tributaries are monitored for quality by Natural Resources Wales. The river is routinely polluted by Dŵr Cymru sewage treatment plants and agricultural runoff. Algae blooms are common during the summer months. The river quality tends to be acidic in the headwaters with very low concentrations of the common anions and cations. Natural Resources Wales monitors water levels in the valley, with a view to giving flood