The Bulgarian clues for the first stop Literature

The three clues about the Bulgarian mystery historical town:
1. The students of the creators of the Cyrillic alphabet used to work there.
2. It is connected with the name of King Simeon I (10th century), during his reign the Bulgarian country bordered on three seas.
3. This town was one of the former capitals of the first Bulgarian state on the Balkan Peninsula.

THE MYSTERY TOWN
You start from Sofia and travel to the north-east of Bulgaria. On your way you pass through the town of Veliko Turnovo. It is the second Bulgarian capital. The books written in the Turnovo literary school put the foundations of the contemporary Slavic literary language. The Old-Bulgarian book is hand-written and extremely precious with its miniatures (with multi-coloured compositions), the Tetraevangelia of Ivan Alexander known as the Gospel of London which still decorates the British National Museum as well as the chronicle of Manasii –kept in the Vatican.
Then you should pass through the town of Shoumen. The mystery town is located at about 20 km., south-east of the town of Shoumen.
The mystery town became the first Bulgarian capital during the reign of King Simeon. The first literary school was established at this place. The importance of its activity marked the beginning of the Golden Age in the cultural history of Bulgaria. Some of the most famous writers and teachers that worked there are Naum Preslavski, Chernorizets Hrabar and Joan Ekzarh.