Vanilla and Rise and Fall
- Cannot be adjacent to another Monastery.
Before the release of Gathering Storm, the Monastery is a largely useless improvement even for a Religious Victory player. A yield of 2 Faith per improvement is negligible, and withdrawing all your religious units to your territory to heal up is impractical when considering how narrow the window of opportunity for a Religious Victory is. On a Standard-sized or larger map, no one should ever spend turns to march their religious units to a civilization halfway across the map, get them damaged, march them back home to heal and mobilize them again. Armagh's Suzerainty, therefore, should almost always be dead last on your priority list.
After the release of Gathering Storm, however, the Monastery receives a buff that makes it actually useful: it provides +1 Housing per improvement (+2 Housing with Colonialism, as long as it's within 3 hexes of a City Center) with additional Faith based on adjacent Districts. Remember, 1 Housing in the early game is worth 2 Farms, Plantations, Pastures, and/or Camps, and this improvement can be placed on any land tile not adjacent to another Monastery, unlike many other civilizations' unique tile improvements. The Monastery alone can pretty much single-handedly solve every Housing issue that a civilization can run into, so civilizations with Food bonuses like India, the Khmer, and the Inca should definitely compete for Suzerainty of Armagh.
A monastery, in the Roman Catholic tradition, is a complex of buildings that serves as communal home and workplace for monks (and nuns, in modern usage termed “convents”). These also include someplace reserved for prayer, such as a chapel or church. And many housed hospitals, schools, distilleries, and more. According to legend, Christian monasticism began in Egypt, although the first monastery in Europe was founded c. 344 AD near Chirpan (Bulgaria) by St. Athanasius. A couple centuries later, in 529, Saint Benedict established the monastery at Monte Cassino, laying the pattern for Catholic monasticism. Monasteries soon began appearing all over Europe, and beyond.