seaside town, Denbighshire (Sir Ddinbych) county, historic county of Flintshire (Sir Fflint), Wales, at the mouth of the River Clwyd. The town is predominantly a holiday resort, with extensive sandy beaches and excellent rail and road links with Lancashire and the English Midlands. Its promenade stretches for 3 miles (5 km), with a domed pavilion and the all-glass Royal Floral Hall. Prestatyn, which adjoins Rhyl to the east, is a similar holiday resort. Prestatyn has remains of prehistoric settlement, Offa's Dyke (8th century), and a demolished castle (12th century). Pop. (2001) 25,390.