7.5 km west of the present town of Karnobat is one of the most impressive medieval monuments throughout South Bulgaria – powerful medieval fortress Markeli. City of Markeli is a strategic point, located on the important road between Old Bulgarian political centers of Pliska and Preslav – Danube. From the standpoint of Bulgarian military political history and culture of the First Bulgarian Kingdom most fascinating moment in the history of Markeli is its transformation from early Byzantine city to proto camp of Khan Krum in 811 year. Here is built Old-bulgarian Camp, where Bulgaria develops advances against Byzantium – Adrianople, Constantinople.