Stand at what survives of the keep and work out the shape of the original from two towers

Find out how an 1814 renovation with explosives destroyed a castle six centuries old

Go into VISUAL, the contemporary art gallery and theatre in the town

Carlow Castle is thought to have been built by William Marshal between 1207 and 1213 and it was the first of its kind in Ireland — a towered keep, a great rectangular block with four three-quarter-round towers at its corners, walls 2.7 metres thick. It survived six centuries. Then in 1814 a man converting it into a lunatic asylum decided to make more room inside by using explosives, and brought most of it down. Two towers and one wall are all that is left, standing beside the Barrow in the middle of the town.

Carlow Castle: The First Towered Keep in Ireland

Photograph the capstone from ground level with a person in frame to show the true scale

Find the portal stones and identify the burial chamber entrance

Walk the full perimeter of the structure and count how many support stones are still in place

A portal tomb whose capstone, estimated at 150 tonnes, is reputed to be the heaviest in Europe — propped on its portal stones at one end and sloping to the ground at the other, in a field outside Carlow town for some 5,000 years. Free, five-minute walk from the car park, and almost nobody knows it exists.

Brownshill Dolmen

Walk right round the burnt-out shell and count the different shapes of tower

Go through both of the interconnecting walled gardens behind the house

Find out what is known about the fire of April 1933 — the cause was never established, and the inside of the shell is not accessible

Look at how much Gothic detail survives on a ruin nobody has restored

From the mid-1820s the English architect Thomas Cobden rebuilt Duckett's Grove for John Dawson Duckett in castellated Gothic revival, piling on towers and turrets — round, square and octagonal — until the house looked like several castles arguing with each other. It burned overnight on 20 April 1933 and was never rebuilt. The shell still stands, and the two interconnecting walled gardens behind it are run by the county council as a public park, free to walk into.

Duckett's Grove: A Burnt Gothic Shell in Carlow

Walk into the square granite courtyard and pace out the 80 feet each way

Find the doors and fireplaces still readable in the foundations

Work out why a castle would be built with no keep and no corner towers

Look at the granite courses and decide for yourself whether it was ever completed

Ballymoon stands in a field three kilometres east of Bagenalstown and it is unlike any other castle in Ireland: a perfect square courtyard about 80 feet on each side, walled in granite 20 feet high and 8 feet thick at the base, with no keep and no towers. The buildings ran round the inside of the wall, and you can still read the doors and fireplaces in the foundations. It is thought to be 13th-century, and it may never have been finished. Nobody is certain who built it or why.

Ballymoon: A Square Castle That Was Never Finished

Stand under the Moone High Cross, the second-tallest high cross in Ireland

Find Daniel in the lions' den and the three children in the furnace

Find the five loaves, the two fish and the two eels

Look for the fragments of other crosses in the abbey grounds

In the ruins of the early monastic site of Moone Abbey, on the River Greese in south Kildare, stands the Moone High Cross. It is granite, 17.5 feet high with its base, the second-tallest high cross in Ireland and one of the best preserved, and it lay buried in pieces until two sections were dug up in the graveyard in 1835. Its panels show Daniel in the lions' den, the three children in the fiery furnace and the Crucifixion, with the apostles set out in rows below it, and the feeding of the five thousand simplified to five circles for the loaves, two fish and two eels that are not in the Bible. A roof now protects it from the weather.

Moone: The High Cross With the Five Loaves and Two Eels

Walk round Altamont's lake, dug as Famine relief work in the 1840s

Take the family-led tour of Huntington Castle

Walk the yew walk at Huntington, older than the castle

Altamont, between Tullow and Ballon, has 40 acres of gardens, the Ice Age Glen and walks down to the Slaney. The house goes back to the 1720s; in the 1840s the Dawson Borrer family had the lake dug as relief work during the Famine, and in the 1920s Fielding Lecky Watson grew the azaleas and rhododendrons round it from seed. Corona North left it to the state before she died in 1999, and it is free to enter. Down the road at Clonegal, Huntington Castle was built in 1625 by Sir Laurence Esmonde to guard the Wexford road, and the same family line has lived there ever since; its yew walk is older than the house, and in the 1970s its basement became a temple to Isis.

Altamont and Huntington: Two Carlow Gardens

Look up at the Romanesque doorway and find the capitals carved as human heads with intertwining hair

Walk right round the tower and look at how little of it beyond the 19th-century cap has ever been rebuilt

Find the ruined church and castle remains beside it on the green

Look at how the whole monastic site now sits in the middle of an ordinary village

St Mochua founded a monastery at Timahoe in the 7th century, and the records of it are violent and matter-of-fact — a church burned here in 919, a murder in a church doorway in 1019. The round tower that stands on the green now was built in the mid-12th century and is one of the finest in Ireland, and what makes it exceptional is the doorway: set high off the ground and elaborately carved in the Romanesque style, with four orders of decoration separated by a narrow vaulted lobby, and capitals carved as human heads with their hair intertwining.

Timahoe: The Round Tower With the Carved Doorway

Walk under the sixteen limestone arches of the 1860 viaduct

See Borris House, held by the MacMurrough Kavanaghs in an unbroken Gaelic line

Walk a stretch of the Barrow Way below the village

Look up at Mount Leinster from the village street

Borris House is the ancestral home of the MacMurrough Kavanaghs, who claim descent from the kings of Leinster — one of the very few Gaelic families to hold their land right through. Below the village runs the viaduct locals call the Sixteen Bridges: sixteen arches of limestone built in 1860 to a design by William Richard Le Fanu, carrying a railway that no longer exists across the valley. The village also has one of the oldest golf courses in Ireland.

Borris: The Sixteen Arches and the MacMurrough Kavanaghs

Walk the monastic site and compare it with the plan drawn in the Book of Mulling

Climb the Norman motte beside the monastery

Find the line of St Moling's watercourse, said to have taken him seven years to dig

Walk down to the Barrow at the foot of the village

St Moling, who died in 697, founded a monastery on the Barrow here in the 7th century, and the Book of Mulling, written here in the late 8th or early 9th century, carries a drawing long read as a plan of this monastery, showing four crosses inside and eight outside a circular wall, read as the earliest surviving plan of an Irish monastery. The story goes that Moling dug a mile-long watercourse with his own hands to power his mill, and that it took him seven years. The site holds the monastic ruins, a Norman motte and a graveyard still used.