Pick a county to see everything this site lists there: holy wells and their pattern days, round towers, high crosses, ogham stones, mass rocks, sweathouses, castles, lighthouses, award beaches and national parks. Every entry links to the record or page it came from, most with a map link.
Or open a county's own page:
Source: National Monuments Service, Archaeological Survey of Ireland, Sites and Monuments Record, open data via data.gov.ie ↗ (CC BY 4.0); every record links to the Historic Environment Viewer ↗. Northern Ireland: Northern Ireland Sites and Monuments Record (Department for Communities, Historic Environment Division), OpenDataNI ↗.