I know that when visiting the Vatican or churches that proper attire is necessary. All of the suggestions I've read emphasize that shoulders (and sometimes the head) must be covered, as well as knees -- so no shorts or short skirts. But this is rather general, IMO.
I want to know if women should wear skirts or if slacks are appropriate. Even jeans? How about for men? Obviously slacks, no shorts, but jeans for them if worn with a shirt nicer than a t-shirt? For all I know even t-shirts would be acceptable.
On Carnival's website, in looking at the shore excursions in Istanbul and Izmir, it notes that you will be requested to remove your shoes before entering mosques and to wear socks. I normally wear sandal-like shoes without socks, but if I wear such shoes will it be ok if I have knee-high hosiery on instead of actual socks??
Woman: nothing too short and open for views!
Man: nothing too short and open for views!
You must not be dressed like you are going on a funaral or wedding. But a certain kind of respect should be shown.
Especially when you walk into the basements to see the gravestone of John Paul II. - everybody is well dressed there, and pray for him. And if you want to feel comfortable you should wear something which fits.
At the Vatican, the strict dress code pertains to St. Peter's Basilica. So anyone going unprepared, you may still tour the museums and other areas which don't have the dress code. But, a visit to the Vatican wouldn't be complete without the visit to St. Peter's even for those of us who are not Catholic. Yes it is a place of worship so you must be respectful in manner and dress. But many people do at the last minute throw on a wrap around shawl or skirt around their waste (even a blanket) or a shawl over their shoulders. I don't mean any disrespect to the previous poster or anyone else reading this but it is a major tourist attraction so the security is mainly concerned with what is showing, not exactly what you are wearing to cover it up. Men definitely cannot wear shorts, even below the knees. The first time we visited, I was not allowed so we had to return the next day. Many other churches in Europe allow long shorts, not the Vatican. Bring a pair of warmups or thin pants to wear over your shorts. T-shirts are definitely allowed. Yes, you don't have to wear a suit or dress, but we've seen many fashion statements not showing shoulders or knees.
But you MUST visit there. And don't miss the Sistine Chapel, absolutely breathtaking, in my opinion of course.
Oh, you may have guessed, but just to confirm, we visited in the middle of summer. So I don't know if security may have some leeway knowing people are dressing to be cool. Probably in cooler months people will be wearing long pants and shirts/tops anyway, so no problem.
At the Blue Mosque in Istanbul, shoes must be removed. I was wearing nylon ped-type socks, and that was fine. Also, they make some women cover their hair (with a provided scarf if you don't have one, yuck). Thankfully, I had my own. I don't know how they decide who does and doesn't cover their hair. They didn't make the brunettes around me. I'm a redhead. The Hagia Sofia is a museum, so the shoe and scarf rules don't apply there.
In Izmir, the only religious site I visited was the House of the Virgin Mary. There were no dress code rules. I will say that it was very hot at Ephesus though.
This was my second visit to a Muslim country (Malaysia was the other). Regardless of rules, I tried to dress with respect for the culture. I never wore anything sleeveless and wore skirts/dresses that were midcalf-length. I think I received better treatment from locals by doing this.
I hope this was helpful.
Oh, and I echo the above comments with regard to the Vatican. And I did see people turned away at St. Peter's for improper dress.