Corpus Domini, also known as Corpus Christi, is a Christian feast that celebrates the Real Presence of the body and blood of Jesus Christ in the Eucharist. In Vatican City, as in many parts of the Catholic world, this feast is an important solemnity and is typically observed on the Thursday following Trinity Sunday, although some countries may celebrate it on the subsequent Sunday to allow more worshippers to attend.

History:

• The Feast of Corpus Christi was instituted by Pope Urban IV in 1264 following reported miracles and intense devotion to the Holy Eucharist.
• It was encouraged by visions experienced by Saint Juliana of Mont Cornillon, who had a great reverence for the Blessed Sacrament.
• The papal bull "Transiturus de hoc mundo" established its celebration throughout the Latin Church.

Traditions:

• The day is marked by a special Mass celebrated by the Pope in St. Peter's Basilica or another Roman church.
• A traditional Eucharistic procession through the streets of Vatican City follows, with the Pope or a representative carrying the Blessed Sacrament under a canopy. This procession symbolizes bringing Christ into the world.
• The faithful often participate in acts of adoration such as spending time in Eucharistic adoration before or after Mass.

Activities:

• Catholics may attend Mass and receive Communion on this day as an expression of their faith in the real presence of Jesus in the Eucharist.
• They participate in processions that are often elaborate and accompanied by hymns and prayers.
• Some decorate altars on their homes' exterior for processions to stop and adore, embellished with flowers and candles.

In Vatican City, Corpus Domini remains a significant day where believers join together to honor one of their most profound mysteries - that bread and wine are transformed into Christ's body and blood during Mass.