What other holy cities besides Mecca are located on the Arabian Peninsula?

Besides Mecca, the Arabian Peninsula is home to Medina, another significant holy city in Islam. Medina is known as the site of the Prophet Muhammad's mosque and his burial place. Additionally, cities like Najaf and Karbala, while primarily associated with Shia Islam, are also significant pilgrimage sites, though they are located in Iraq, which is adjacent to the Arabian Peninsula.