Coleraine

A crossing of the lower Bann near where Mount Sandel stands — the oldest known human settlement in Ireland, dated to about 7000 BC. The town itself was laid out by the Irish Society of London during the plantation.

Mount Sandel, on the edge of Coleraine, is one of the oldest known settlements in Ireland, dating from about 5935 BC. The town's name, Cúil Raithin, the nook of ferns, comes from a story in the 9th-century Tripartite Life: when Patrick came, the local chief Nadslua offered him ground by the Bann to build a church, a spot overgrown with ferns that boys were burning for fun.

Coleraine was one of the two towns the London companies built in the Plantation of Ulster, and the Irish Society is still responsible for much of it; its slightly skewed street plan and traces of its ramparts are from that time. In 1689 it held out against a Jacobite attack before its Protestant defenders withdrew to Derry. In the 19th century it grew with the port, the railway and a large distillery, and in 1968 the New University of Ulster opened here. On 12 June 1973 an IRA car bomb on Railway Road killed six people.

Drawn from the History section of the Wikipedia article on Coleraine ↗, rewritten here and adding nothing it does not say; licensed CC BY-SA 4.0.

• Killowen Castle · castle · under 1 km
• Coleraine Castle · castle · under 1 km
• Low Rock Castle · castle · 6 km
• Dunluce Castle · castle · 10 km

Straight-line distances from the town centre, from each site's documented coordinates.

• Mount Sandel · Ireland's oldest known settlement — where hunter-gatherers built huts above the Bann around 7000 BC. There is nothing to see but the view; that is the point.
• Dunluce Castle · MacDonnell stronghold on a sea-stack; in 1639 the kitchen fell into the sea, cooks and all. The lost town beside it was only found in 2011.
• The Giant's Causeway · Built by Fionn to cross to Scotland and fight the giant Benandonner — who fled back and tore up the road when Fionn's wife showed him 'the baby' (Fionn in a bonnet).

All of these are pinned on the Hidden Ireland map.