On the top of one of the Neapolitan hills, the Church of the Certosa di San Martino is a casket to one of the city's greatest treasures. Built in 1325 at the behest of the Duke Charles of Angiò, it was the mother church of the Order of the Certosini. After gathering with your guide outside the front of the church, enter the structure for a 2-hour guided tour. Around the cloister of the Monastery, the small cells demonstrate the need for peace and prayer sought by all monks. The great renovation of 1590 led the church of the Certosa to be one of the largest artistic construction sites in Southern Italy. Workers from Rome and from all parts of the Viceregno were charged with renewing the great church. These works lasted for about a century, with several interruptions and modifications in between. Today it is obvious that these works paid off. From the vault to the wonderful floor, each side chapel and every room is a priceless treasure. The beauty here is overwhelming from the inside out, with the city skyline looking crisp and wonderful on sunny days, and poetic and fascinating even in the rain.