The first city to collect and compile Hadith was Madinatul’ Munawarrah ~ The Illuminated City.
Imam az-Zuhri was one of Imam Malik’s teachers and he would go over the Ahadith with the Imam to make sure he recited everything correctly. Kind of like, how Imam Malik would check his Quranic recitation with Imam Nafi.
The Caliph ‘Umar ibn Abd al-Aziz used to say:
“Take the Knowledge from Imam ibn Shihab az-Zuhri, for you will not find any one who knows about the previous year more than him.”
“The first one to write down Hadith {as to preserve them} was Imam ibn Shihab az-Zuhri at the turn of the 1st century by the order of ‘Umar ibn ‘Abd al ‘Aziz.”
{Fath al-Bari ~ Explanation of Sahih Bukhari}