Medina is generally considered to be the "cradle of Islamic culture and civilization".^[4] The city is considered to be the second-holiest of three key cities in Islamic tradition, with Mecca and Jerusalem serving as the holiest and third-holiest cities respectively. Al-Masjid al-Nabawi (lit. 'The Prophet's Mosque') is of exceptional importance in Islam and serves as burial site of the last Islamic prophet, Muhammad, by whom the mosque was built in 622 CE (first year of the Hijrah). Observant Muslims usually visit his tomb, or rawdhah, at least once in their lifetime during a pilgrimage known as Ziyarat, although this is not obligatory.^[5] The original name of the city before the advent of Islam was Yathrib (Arabic: يَثْرِب), and it is referred to by this name in Chapter 33 (Al-Aḥzāb, lit. 'The Confederates') of the Quran. It was renamed to Madīnat an-Nabī (lit. 'City of the Prophet' or 'The Prophet's City') after Muhammad's death and later to al-Madinah al-Munawwarah (lit. 'The Enlightened City') before being simplified and shortened to its modern name, Madinah (lit. 'The City'), from which the English-language spelling of "Medina" is derived. Saudi road signage uses Madinah and al-Madinah al-Munawwarah interchangeably.^[5]