The paleo- christianic basilicas and the chapels dispersed in the island of Nisyros containing famous frescos with a particular archaeological and tourist interest, mark its strong Byzantine presence. The approach of these chapels is made through picturesque paved paths.

In the island of Nisyros you can also find numerous and important monasteries:
The monastic compound of Stavros (Holy Cross) is located in the elevation located in the western party of the Lakki valley (Volcano) and celebrates the memory of its protectors in the 14th of September.

The Monastery of Panaghia Kyra (Our Holy Lady) is located in a region of an exceptional archaeological significance. It celebrates the memory of Panaghia Kyra in the 23rd August.

The Monastery of Aghios Ioannis the Theologue is located in the village Nikeia celebrates the memory of its saint in the 26th of September.

The Monastery of Evangelistria which is located only at 4 kilometres away of Mandraki celebrates the memory of the Holy Virgin the Evangelistria the Tuesday after the day of Easter.

The most important monastery is the one of Panaghia Spiliani (Holy Virgin of the Caves) which is built in a cave dominating the village of Mandraki. The main temple of Panaghia Spiliani is dedicated to the Assumption of the Holy Virgin whereas the adjacent chapel is dedicated to Saint Charalambos. The icon of Panaghia Spiliani is famous as well as the abundant silver and gold relics. The abundant collection of relics and precious art and the library with its rare editions are also important. The Monastery of Panaghia Spiliani constitutes the religious symbol of the island whereas the popular feast of the 14th and 15th August attracts visitors from the whole Dodecanese.