Knocknarea is a large prominent hill west of Sligo town in Ireland, with a height of 327 metres. On the summit of Knocknarea is a large cairn about 55 metres wide and 10 metres high, making it the largest cairn in Ireland outside Brú na Bóinne in Meath. Although it has not been excavated by archaeologists, it has many features of a classic passage tomb.
The cairn is flat-topped and several kerbstones can be seen on the northern side. It is believed to date to around 3000 BCE, during the Neolithic (New Stone Age). It is known in Irish as Miosgán Meadhbha (Meadhbh's heap), and in English as Maeve's Cairn or Maeve's Tomb. Meadhbh is a queen of Connacht in Irish mythology, who is believed to have originally been a goddess.
The ancient cairn is a protected National Monument. In recent years, archaeologists have warned that it is being eroded by hikers climbing on it and moving or removing stones. The large number of climbers is leaving scars on the cairn and may be destabilizing the tomb inside. Irish folklore holds that it is bad luck to damage or disrespect such tombs and that doing so could bring a curse.
References:The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.