Hi, I was intrigued to see your photo. I came upon what I think is the same structure a few months ago and it hadn't been registered on the National Monuments database. I've since registered it. It doesn't appear to be at all well known locally - did you speak to anyone about it when you were travelling or did you just find it by chance? It may of course be a very similar one. The one I found was at E: 585472, N:904051 - the area looks like it could have more but your image is very similar to the one I found, must be the same!
I slept there for one night and in the morning there were a lot of cows around our tent...
Third from west in a row of 6 portal tombs at Malin More in County Donegal
This photo is mislocated in the middle of the NUIG campus. Castlegar is located on the other side of the river, at 53 17'54.91" N 9 01' 16.90" W.
On Google Earth the outline and shadow of the two remaining sides of Castlegar can be seen at that location, along with the attached handball court between the castle & the road. This photo was taken from 20-30 meters WSW of the castle.
Megalithic tomb in the middle of the Burren, County Clare. Note the pied wagtail sitting on top. With the sun hitting this right, from a kilometer away it appears to be a house.
Only one third of Seefin Castle remains. The doorways open out from the circular stairway. There are also openings from the stairway into the floors of the remaining third of the tower.
Castle overlooking Tierneevin Lough near the County Galway - County Clare border.
All that remains of the Ardrahan Round Tower is a few courses of stone which have become part of the cemetery wall.
Queen Maeve, legendary Queen of Connacht, is reputed to be buried in this cairn. According to Herity, in "Irish Passage Graves" (1974) the mound probably hides a passage tomb.
I was just checking this area and noticed the incorrect location for these photographs. I hope the remarks are of some help.