"Entry to the Vatican Museums, the Sistine Chapel, St. Peter's Basilica and the Vatican Gardens is permitted only to appropriately dressed visitors.
Low cut or sleeveless clothing, shorts, miniskirts and hats are not allowed."
http://www.museivaticani.va/content/museivaticani/en/visita-i-musei/consigli-utili.html
Undvik alltså linne, urringningar, shorts, kort kjol och keps så går det bra!
Holmpo