In any culture you visit, respectful to be aware and follow some of the religious customs in that country. In Pakistan this can go one step further in that some of the religious customs are law, and not following them can get you ejected from certain places or even arrested. While some rules are only relevant in certain areas, some are country wide, so it's a good idea to know them before you visit. Islamabad is one of the more liberal cities of all Pakistani cities as far as cultural rules are concerned because many foreigners live there. It's still better to be prepared, and to follow the rules just in case.
The one thing you'll notice in Islamabad is that shorts and skirts are nowhere to be found. Both men and women are expected to be covered well below the knee. Revealing tops are also unacceptable. Women are not always expected to cover their heads in public, particularly if you're a foreigner. It is still a good idea for women to carry a scarf as some buildings, particularly mosques, require that women cover their heads upon entry. If you are wearing western clothing, expect people to stare at you.
Two things you will never find on any menu in Pakistan is wine and pork. Pork is guaranteed not to be found anywhere, even hotels do not serve it. There is often substitutions available in the form of turkey bacon and other alternatives. Wine on the other hand can be found in some places, hotels being the most common. If you have your own wine, some restaurants will allow you to bring it into the restaurant, however discretion must be taken.
As with all Muslim countries prayer time is very important. You'll know that it is prayer time by the various calls to prayer coming from the mosques around town. Friday afternoon is the most important religious time of the week, and you'll find some stores and restaurants may be closed. During any prayer time mosques are closed to all tourist.
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