The Pontifical Swiss Guard is a group known for standing guard at the entrances to Vatican City. Their main job is to provide security and protect the Pope. They can easily be recognized by their distinctive uniforms, which are very colorful and look much like the clothing worn by soldiers during the Renaissance era.
The Pontifical Swiss Guard holds the title of being the smallest and oldest standing army in the world. This tradition began in 1506 when Pope Julius II officially founded the Guard. However, the use of Swiss soldiers by the popes dates back even further. During the 1400s, Swiss mercenaries were often brought to Rome to serve as bodyguards for the pope and to provide extra security.
Source - https://en.wikipedia.org/wiki/Swiss_Guard