St Tanwg's Church sits low in the dunes at Llandanwg, just south of Harlech, and feels much older and quieter than the castle above town. Parts of the small stone church are medieval, and the site is traditionally linked with early Christian worship on this coast.
It is worth combining with a beach walk rather than treating it as a separate trip. The appeal is the setting: sea air, sand, old stone, and the sense that this coast has been occupied and prayed over for a very long time.