Fairy mounds are spread out all acorss Ireland and they appear as small hills within the ground. There is even today still much supertision and myth revolving around these mounds, and even today the people of Ireland respect the fairy mounds and do not think they should be disrupted in anyway, because the beielf in what they call the "wee people" is still very strong there. The "wee people" can refer to a varity of different things, from faries to elves, or leprichons, etc...
The fairy mounds are thought to be sacred to the fae race, and is reguarded as thier dwelling place. There are many myths surrounding these mounds. It is said they act as portals, and homes to the fae whom dwell inside.
They are also considered to be the dwelling place of the sidhe who are invisable magickal beings, formaly known as the Tuatha before they were driven into the underworld.
More moden day evidence suggusts that the fairy mounds were originaly used as sacred burrial sites for ancient poeples.