Have you ever wondered what these round towers were for, who used tower houses or what an Ogham-stone is? All are relics from the Irish middle ages, dozens of them are literally dotted around Ireland. These are (in alphabetical order) the most important medieval attractions you will find:
Small monastic buildings erected from rough stones, built to a round floorplan and with a cupola-like roof ... making them look like gigantic beehives. They are typical of Celtic monasteries and may have been used by monks or as visitor's quarters. Excellent examples may be seen on the Dingle Peninsula.
Castles - Motte and Bailey
Early Norman fortresses erected to secure the surrounding countryside and provide a well-defensible shelter in case of attacks. Consisted of a "motte" (an artificial, steep hill) with a tower on its top, the whole surrounded by a defensive pale, the "bailey". The mottes are still visible and instantly recognizeable in many places. On a curious note - the passage tomb at Knowth was re-used as a motte.
Castles - Norman
From the 13th century onwards massive stone castles replaced the smaller, weaker motte and bailey castles. These are the classical castles combining a seat of power with a military base. Impressive structures can be found in Carrickfergus, Limerick and especially Trim.
Castles - Ten-Pound-Castles
Small castles, very similar to tower houses, that were mainly built to take advantage of royal subsidies - king Edward VI in 1429 guaranteed a certain income for anyone building a castle to defend the "pale" (the area of English rule in Ireland).
The usual Latin cross with a circle connecting the arms to the upright post became known as the "Celtic cross". The significance of the added circle is unknown - it might be a representation of a halo, it might be a nod to an earlier, sun-worshipping tradition. Or it might simply have been a stonemason's clever design idea to make the arms less likely to break off.
After Saint Patrick's mission Christianity was following a strict episcopal system, this changed in the 6th and 7th centuries with the church developing into network of monasteries. These were small communities of their own, their prominent buildings including beehive huts, high crosses, oratories and round towers. The former monastic settlements at Clonmacnoise and Glendalough are especially worth a visit.
Churches - Early Christian and Romanesque
Ireland's earliest churches were built from wood, none survive - stone churches were built from the 9th century onwards, very simple structures like Columba's House in Kells or the Gallarus Oratory on the Dingle Peninsula. From the 12th century onwards churches were built in the romanesque style. This marked the change (back) from a monastic to an episcopal organization. Note that romanesque churches in Ireland are significantly smaller than elsewhere, most being shorter than 40 feet.
Churches - Gothic
Gothic churches, abbeys and monasteries were erected from the 12th century onwards, mainly influenced by the influence of foreign ecclesiastical orders like the Augustinians, Cistercians and Franciscans. These strictly organized orders replaced the Celtic-Irish monasteries and brought the new architectural style with them. Very interesting examples are Jedburgh Abbey and Mellifont.
Crosses, Grave Markers and Fonts
All sorts of medieval artifacts can be found in Irish churches, churches and museums - some severely weathered and almost unrecognizable, some in full splendor (even in ruined churches). Especially grave slabs with portraits of the deceased are interesting - the most famous being on Strongbow's tomb in Dublin's Christ Church Cathedral. From the 15th century richly decorated tombs, often with apostles and saints on the sides, became fashionable.
Grave slabs used between the 9th and 12th century, sporting richly decorated cross motifs. Plus the name of the deceased and a request for a prayer.
High crosses are massive (and really high) stone edifices in the classic shape of the Celtic cross and bearing rich decorations carved into the stone. These are knotwork, geometrical decorations and illustrations. In the first heyday of high crosses around the 9th century biblical motifs were used. During the 12th century depictions of Christ and local saints became more popular. Especially the biblical scenes were used as a teaching aid by monks and would have been painted in bright colors. Fascinating high crosses can be found in Kells, Monasterboice, Clonmacnoise and Kilfenora in the Burren.
Standing stones bearing inscriptions in the ancient Ogham-system, a special written language mainly used in Ireland. Unfortunately the inscriptions are generally very short and not very interesting. Ogham stones form a "bridge" between pre-historic Ireland and early Christian times.
The high, circular buildings were usually erected next to monasteries or churches and would have served as a marker in the landscape as well as a bell tower. The might have been used as lookouts and treasure houses as well - which might be the reason why many were destroyed and burnt down by raiders. Some great round towers can be found in Kells, Monasterboice and Clonmacnoise.
Basically these are houses built in the design of a strong, defensive tower. Not things of beauty but practical and safe homes in a rough neighborhood. A number of the forbidding tower houses were later converted, Leahmaneagh in the Burren and Donegal Castle being prime examples. The tower house most accessible to tourists would be Ashtown Castle in Dublin's Phoenix Park.