Kilmainham Gaol

Home to an extensive collection of medieval architecture and Celtic art, this enormous compex has everything you could want in a castle experience. Along with the 90-foot round tower dating back to 1100, some of the other structures you’ll see are the 12th-century Cormac’s Chapel that’s home to one of the period’s best-preserved Irish frescos and the 13th-century cathedral.

Cities and towns list

1st, Dublin

2nd, Cork

3rd, Limerick

4th, Galway

5th, Waterford

6th, Drogheda

7th, Swords

8th, Dundalk

9th, Bray

10th, Navan

11th, Kilkenny

12th, Ennis

Saint Patrick's Day is a public holiday in the Republic of Ireland,^[10] Northern Ireland,^[11] the Canadian province of Newfoundland and Labrador (for provincial government employees), and the British Overseas Territory of Montserrat. It is also widely celebrated by the Irish diaspora around the world, especially in the United Kingdom, Canada, United States, Brazil, Argentina, Australia and New Zealand. Saint Patrick's Day is celebrated in more countries than any other national festival.^[12] Modern celebrations have been greatly influenced by those of the Irish diaspora, particularly those that developed in North America. However, there has been criticism of Saint Patrick's Day celebrations for having become too commercialised and for fostering negative stereotypes of the Irish people.

Ha'penny Bridge

Inside the town walls Navan consisted of three streets. These were Trimgate Street, Watergate St. and Ludlow St. (which was once called Dublingate St.)

https://en.wikipedia.org/wiki/Navan 

Kilkenny is a medieval town in southeast Ireland. Its grand Kilkenny Castle was built in 1195 by Norman occupiers. The town has deep religious roots and many well-preserved churches and monasteries, including imposing St. Canice’s Cathedral and the Black Abbey Dominican priory, both from the 13th century. It's also a crafts hub, with shops along its winding lanes selling pottery, paintings and jewellery.

https://en.m.wikipedia.org/wiki/Martello_tower
They stand up to 40 feet (12 m) high (with two floors) and typically had a garrison of one officer and 15–25 men. Their round structure and thick walls of solid masonry made them resistant to cannon fire, while their height made them an ideal platform for a single heavy artillery piece, mounted on the flat roof and able to traverse, and hence fire, over a complete 360° circle. A few towers had moats or other batteries and works attached for extra defence.

The Martello towers were used during the first half of the 19th century, but became obsolete with the introduction of powerful rifled artillery. Many have survived to the present day, often preserved as historic monuments.

In the second half of the 19th century, there was another spate of tower and fort building, during the premiership of Lord Palmerston. The Palmerston Forts are also circular in design and resemble Martello towers.