A massive LEGO model of the Vatican is on display at the Franklin Institute in Philadelphia in honor of the Pope’s upcoming visit to the United States.

Father Bob Simon spent about ten months creating this brick version of St. Peter’s Basilica and St. Peter’s Square, the Associated Press reports. He began construction in his rectory at the St. Catherine of Siena church in Moscow, Pennsylvania, (about 100 miles north of Philly), basing the model off of a book cover image and watching YouTube videos to figure out how to make the basilica’s round shape.

While he is not sure how many pieces he used to make this replica, he told CBS Philadelphia that he may have used as much as half a million— including about 44,000 cobblestones in the square, “6,000 round bricks that make up the colonnade” and “12,000 2×2 tiles” under that.

The sculpture is part of an exhibit on the history of the Vatican opening at the Franklin Institute on Saturday.

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Write to Olivia B. Waxman at olivia.waxman@time.com.

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