1. Passage Tombs
The jury is still out whether these tombs or "burial mounds" were originally built for a funerary purpose, but they practically litter the landscape, often in mysterious clusters. Launching theories of "sacred landscapes" and ley lines.
2. Stone-Built Oratories
The first churches in Ireland were far from splendid Gothic cathedrals, they were instead solidly built of local, rough-hewn stone. Huddling into the landscape to withstand wind and weather. Always a consideration in Ireland.
One of the most famous is the Gallarus oratory on the Dingle Peninsula.
3. Round Towers
Round towers are the definite native architecture of Ireland - they immediately pinpoint the location and are virtually unique to the country. They are unmissable in many cases, towering over the landscape. Others may be more hard to find.
Find out more about round towers in a dedicated image gallery.
4. High Crosses
High crosses are, strictly speaking, more monuments than architecture, nonetheless they will immediately place you in an Irish (or more broadly "Celtic") frame of mind. Beware, however, of imitations ... not every Celtic cross is a High Cross, an not every High Cross is a Scripture Cross.
Find out more about the origins and forms of high crosses in an in-depth feature.
5. Tower Houses
"My Home is My Castle" ... for many inhabitants of Ireland this was not a saying but a necessity. House-warming parties certainly took on a new meaning when the neighbors arrived carrying torches and swords. Disagreeing about a minor question of land or cattle.
To see a fairly typical tower house one only has to travel to Dublin's Phoenix Park. And there are literally hundreds around the Emerald Isle.
6. Plantation Castles
Plantation castles were, in short, the Scottish take on the venerable tower house - a sturdy home built by Scottish colonists with some st le elements from the "auld country". Many were burned down before the inhabitants managed to really settle down.
7. Great Houses
When Ireland became more peaceful (or the natives were deported to be restless elsewhere), castles became distinctly out-moded and "great houses" were the new must-have of the landed gentry. Which in many cases meant colonialists. Which in turn meant that many great houses did not survive the War of Independence.
Take note that you may also stay in some great houses as a paying guest - a good example is Temple House in County Sligo.
8. Dublin's Georgian Squares
Dublin peaked in the Georgian period, with squares being laid out and grand city dwellings being built. Then at the turn from the 18th to the 19th century this bubble burst - the Irish Parliament voted itself out of existence, politics and big business headed to London and Dublin became a forgotten backwater.
Which actually was lucky as no modern town-planners wielded pickaxes for ages. And Ireland's neutrality in the Second World War allowed all the metalwork to survive - plundered in Britain to aid arms production. Today, especially the Georgian "Doors of Dublin" are a major tourist attraction. Apart from Dublin's own list of signature buildings.