Harlech castle was built between 1283 and 1289 by King Edward I.
Its site was chosen both for its strong natural defences as a high point and for easy access to the sea, which was then much closer to the base of the rock.
Visitors can enter from either the old sea dock area and climb stairs and ramps up to the castle or they can stop at the pay & display lot at the top and enter through the grand gate house.
Harlech Castle opening times are"
April - October: Monday - Sunday 9:00 - 5:00
November - March: Monday - Saturday 9:30 - 4:00 and Sunday 11:00 - 4:00
Also Harlech Castle is closed on December 24-26 and January 1st.
The price of admission is £3.70 per adult with family discounts available. I highly recommend the 3-day or 7-day Explorer Pass if you plan on visiting other Cadw properties.