Just as the city is portrayed as impossibly enormous (12,000 stadia in length, width, and height), so the pearls forming its twelve gates are impossibly enormous (assuming, of course, that the gates are big enough for a person to walk through). But as with so much of the book of Revelation, their size (and hence significance) is symbolic—in this case, depicting the infinite glory of the God of this holy city (Revelation 21:11: “having the glory of God”), that is, the Bridegroom.
21 And the twelve gates were twelve pearls, each of the gates made of a single pearl, and the street of the city was pure gold, like transparent glass.