But a Vatican Museums official says there are no plans to try to limit tourists' access.
Museums director Antonio Paolucci cited concerns about the visitor numbers in an article in the Vatican newspaper on Wednesday, the 500th anniversary of the frescoes' inauguration by Pope Julius II.
Like Julius, Pope Benedict XVI plans to celebrate Vespers in the chapel Wednesday evening.
Paolucci says that sometimes as many as 20,000 people daily visit the chapel. But he says that for the time being "the adoption of a maximum number (of visitors) will not be necessary."
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