Boyle

Built around a Cistercian abbey of 1161 whose church still stands nearly complete, and King House, a great Georgian barracks-mansion. Nearby Lough Key was the seat of the MacDermots, princes of Moylurg, on their island castle.

On 15 August 1599, in the Curlew Mountains above Boyle, Red Hugh O'Donnell's army ambushed and routed an English force under Sir Conyers Clifford at the Battle of Curlew Pass; Sir Robert Cecil counted it one of the two heaviest blows the English suffered in Ireland. The town suffered badly in the Famine. By 1859 it was described as one of the principal towns of Roscommon, with the ruins of Boyle Abbey carefully preserved. In 1917 Count George Noble Plunkett, father of the executed 1916 leader Joseph Plunkett, won North Roscommon in the first Sinn Féin by-election victory after the Rising, with Michael Collins campaigning for him; a plaque on the courthouse remembers it.

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

• Heapstown Cairn · tomb · 14 km
• Rockingham Estate · castle · 4 km
• McDermott's Castle · castle · 5 km
• Ballinafad Castle · castle · 6 km

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

• Carrowkeel passage tombs · Fourteen Neolithic tombs on the Bricklieve ridges, one aligned so the midsummer sunset shines down its passage — the mirror of Newgrange, with no crowds.
• Rathcroghan (Cruachan) · Queen Medb's royal seat: 240 monuments over four square miles, including Oweynagat, the cave called 'the gate to Hell' — one claimed home of Halloween.
• Moytura · Second Battle of Mag Tuired: the Tuatha Dé Danann against the Fomorians. Lugh of the Long Arm kills his grandfather Balor of the Evil Eye with a sling-stone through the eye.
• Rathcroghan — Oweynagat · The 'cave of the cats', birthplace of Queen Medb and doorway to the Otherworld: at Samhain its creatures pour out into the world. One root of Halloween.
• Cruachan — Medb's court · Where Medb and Ailill's 'pillow talk' about whose wealth was greater started the Cattle Raid of Cooley — over one brown bull.

All of these are pinned on the Hidden Ireland map.