Nessebar, Nessebar - this is the city I have been to the most times. I was there for the first time (according to my parents' stories) when I was 3 years old. The tradition of going to the Black sea in Nessebar every year lasted almost 30 years. After that, I also went without my parents, of course.
This is the first UNESCO World Heritage Site I have visited. And to which I always return over the years.
They call Nessebar an "encyclopedia" of Christian church construction. 44 churches from the period from the 5th to the 19th century have been discovered in it so far. (Considering, however, that the island was at least three times as large, it is obvious that the number of churches also exceeded a hundred). Among them are the oldest early Christian basilicas in Bulgaria. Eighteen of the temples are well preserved.
The construction completely stopped during the Turkish slavery (for five centuries only one temple was built), and the existing ones were subject to destruction because the Turks forbade their maintenance.
The churches are scattered all over the town, but it is not difficult to find them - there are information boards next to each one with the basic information about the respective church.
Don't forget to visit the museum, which is immediately after the entrance on the right. Take a full day for walking around the city and visiting the churches so you don't have to rush through the cobbled streets. If you are on summer vacation, use a cloudy or rainy day (if any). Take time to eat at one of the many panoramic restaurants with wonderful views of the sea.