Information from Wikipedia:
Ballynoe boasts two sites of outstanding beauty a stone circle, and a gorgeous tree tunnel leading towards it.
Ballynoe Stone Circle is a stone circle situated in the small hamlet of Ballynoe 2.5 miles (4 km) south of Downpatrick, County Down. It is near the disused railway station, reached by a long footpath off the main road. It is a large and impressive circle lying in cultivated lowland, less than 100 ft above sea level, in the heart of the fertile Lecale peninsula.
It is a large and complex site which appears as a large circle of over 50 closely spaced upright stones, some as much as six feet tall, with some small gaps, surrounding a space about 110 ft across. Two of the fallen stones have cavities which could be artificial cup-marks. The stones of the outer circle are nearly all composed of local Silurian grit, but a few are granite erratics. Two of the stones stand 7 ft apart immediately outside the circle on the west and there are four outlying stones, two on the north-east (9 and 40yd from the circle) and two on the south-west (9 and 50yd from the circle). In the eastern half of the circle is an oval mound contained within a kerb with diameters of 46 and 58 ft, with the long axis on an east-west alignment. Immediately inside the circle on the west, opposite a pair of external stones, is an arc of six stones supporting the edge of a raised platform which occupies much the same position as the oval mound on the east. Excavations found that the 5 ft high mound was of stony earth, with a stone cairn at the core. Under the mound, between the cairn and the kerb were found a number of smooth boulders (baetyls) set in the old surface. Large cists were found at the east and west ends of the mound containing cremated bones.