Cork

Founded as a monastery by St Finbarr on the marshes where the Lee divides, then a Viking port, then a walled Norman town. The city centre is still an island between two channels of the river, which is why its main street curves: St Patrick's Street was laid over an arm of the river. In 1920 Cork lost two Lord Mayors in seven months and watched its centre burned by British forces; since the Civil War it has called itself the real capital.

Cork began as a monastery, reputedly founded by St Finbarr in the 6th century, and grew into a town when Norse settlers built a trading port here between 915 and 922; the monks and the Norsemen seem to have lived side by side, trading with each other. Prince John, as Lord of Ireland, gave the city its charter in 1185, and the walls he knew still survive in places.

For most of the Middle Ages Cork was an English-speaking outpost cut off from Dublin, paying "black rent" to the Gaelic and Norman lords around it to be left alone, and run by twelve to fifteen merchant families who shipped out wool and hides and brought in salt, iron and wine. About 2,100 people lived here, and the Black Death of 1349 killed almost half of them. In 1491 the mayor and leading citizens backed the pretender Perkin Warbeck and were executed for it. The city surrendered to Marlborough in 1690, prospered on its continental trade in the 18th century, and was burned by the Black and Tans in December 1920. In the Civil War anti-Treaty forces held it until the National Army came in from the sea.

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

• Dundanion Castle · castle · 4 km
• Blackrock Castle · castle · 5 km
• Carrigrohane Castle · castle · 6 km
• Blarney Castle · castle · 7 km
• Ballincollig Castle · castle · 9 km
• Belvelly Castle · castle · 12 km

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

• Kindred Spirits, Midleton · Nine great steel feathers in a circle, honouring the Choctaw Nation's $170 gift to Ireland in 1847 — sent sixteen years after their own Trail of Tears.
• Kinsale · Christmas Eve 1601: the Gaelic order's last throw fails in a dawn attack that went wrong. Nine centuries of Ulster kingship ended here, 300 miles from home.
• Spike Island · Monastery, fortress, for a few years in the mid-19th century probably the biggest prison in the British Empire, holding convicts awaiting transportation, then a garrison — 'Ireland's Alcatraz'.
• The Blarney Stone · The goddess Clíodhna told Cormac MacCarthy to kiss a stone before he went to court, and he talked his way out of trouble. Another version puts it before Elizabeth I. The stone was built into the castle in 1446; the legend is first described in print in 1785, so the tradition is younger than the wall it sits in.

All of these are pinned on the Hidden Ireland map.