The foundation stone of the new harbour was laid by the Marquess of Downshire on 1 August 1821. The initial plans and surveys for this ambitious undertaking were made by John Rennie. He, however, died within two months of work beginning, and was succeeded by his son, John, who had as his resident engineer a fellow Scot, the seasoned marine builder, David Logan, who had assisted Robert Stevenson at the Bell Rock Lighthouse (1807–1810). The new harbour had to have greater depth to accommodate steam packets. Rock blasted from the sea bed, within the harbour area and further south in what became known as the Quarry Hole at Meetinghouse Point was used to form the outer slopes of the two piers; but the inner faces were built of limestone from the Moelfre quarries of Anglesea. This 'Anglesea marble' lends itself to the finest ashlar dressing and the new piers remain a triumph of stone carving. The flights of steps display special skill in the deep diagonal binding of each solid step, providing a typically robust engineer's response to the wear of seaboots and waves alike. The harbour consists of two independent piers running north westwards out to sea; parallel nearer the shore, they converge at the outer ends to form a harbour mouth 150 feet (46m) wide. At low tide the water in the harbour is fifteen feet deep.
The foundation stone of the new harbour was laid by the Marquess of Downshire on 1 August 1821. The initial plans and surveys for this ambitious undertaking were made by John Rennie. He, however died within two months of work beginning, and was succeeded by his son, John, who had as his resident engineer a fellow Scot, the seasoned marine builder, David Logan, who had assisted Robert Stevenson at the Bell Rock Lighthouse (1807–1810). The new harbour had to have greater depth to accommodate steam packets Rock blasted from the sea bed, within the harbour area and further south in what became known as the Quarry Hole at Meetinghouse Point was used to form the outer slopes of the two piers; b,ut the inner faces were built of limestone from the Moelfre quarries of Anglesea. This 'Anglesea marble' lends itself to the finest ashlar dressing and the new piers remain a triumph of stone carving. The flights of steps display special skill in the deep diagonal binding of each solid step, providing a typically robust engineer's response to the wear of seaboots and waves alike. The harbour consists of two independent piers running north westwards out to sea; parallel nearer the shore, they converge at the outer ends to form a harbour mouth 150 feet (46m) wide. At low tide the water in the harbour is fifteen feet deep.