You DO need a visa for quite a few Arab countries so the question is justified,
but you can see by checking
http://travel.state.gov/foreignentryreqs.html you do not need a visa for tourist stays in Morocco up to 3 months.
The rock of Gibraltar is a quite bizarre place which is worth while a stay for some hours, you have to get up to the top in order to see the monkeys and have a beautiful look on the straits of Gibraltar from there. The monkeys are not particularly beautiful and spoiled by tourists who feed them, you might want to keep some distance unless you like to get in close touch with them. They don't seem agressive, though.