Following the invasion of the first Arab army in 641 and the relocation of the capital from the Greco-Roman port of Alexandria to the site of present-day Cairo, Egypt was ruled by successive Islamic dynasties, each leaving an architectural legacy. Cairo has more than 600 registered Islamic monuments covering 14 centuries of history. In various states of repair, they are nonetheless an art lover's dream. You can visit the cenotaphs of such diverse figures as the charismatic 19th-century ruler Mohammed Ali, King Farouk, and a ninth-century boy sultan assassinated by his brother. There are also various architectural forms of charity, donated by the sultans, such as student hostels, caravanserai, and sabil kuttab (combined public fountains and Koranic schools). Egypt's mosques generally welcome non-Muslim visitors. Monuments with guardians are open 8 am to 5 pm; many do not require a ticket.