The pearly gates is an informal name for the gateway to Heaven

Heaven

Heaven, the Heavens or Seven Heavens, is a common religious cosmological or metaphysical term for the physical or transcendent place from which heavenly beings originate, are enthroned or inhabit...

 according to some Christian denominations. It is inspired by the description of the New Jerusalem

New Jerusalem

In the book of Ezekiel, the Prophecy of New Jerusalem is Ezekiel's prophetic vision of a city to be established to the south of the Temple Mount that will be inhabited by the twelve tribes of Israel in the...

 in Book of

Book of Revelation

The Book of Revelation is the final book of the New Testament. The title came into usage from the first word of the book in Koine Greek: apokalupsis, meaning "unveiling" or "revelation"...

 . The twelve gates were twelve pearls, each gate being made from a single pearl.

The image of the gates in popular culture is a set of large, white or wrought-iron gates in the clouds, guarded by Saint Peter

Saint Peter

Saint Peter or Simon Peter was an early Christian leader, who is featured prominently in the New Testament Gospels and the Acts of the Apostles. The son of John or of Jonah and from the village of Bethsaida in the province of Galilee, his brother Andrew was also an apostle...

 (the keeper of the "keys to the kingdom

Keys of Heaven

In ecclesiastical heraldry, the Papal coat of arms contain the keys of the office of St. Peter. The Keys of Heaven were, according to Christian tradition, received by Saint Peter from Jesus, marking Peter's ability to take binding actions. Thus, the Keys are seen as a symbol of Papal authority...

"). Those not fit to enter heaven are denied entrance at the gates, and thus descend into Hell

Hell

In many religious traditions, a hell is a place of suffering and punishment in the afterlife. Religions with a linear divine history often depict hells as endless. Religions with a cyclic history often depict a hell as an intermediary period between incarnations...

.