Musala (9,596 ft) is the highest peak in Bulgaria and the entire Balkan Peninsula. Olympus (2,918 m) is the highest peak in Greece and the second highest in the Balkans. Triglav and Korab are the highest peaks in Slovenia and Macedonia, but neither of them is the third or fourth highest peak in the Balkans. ¹⁾

The Gregorian calendar was introduced in 1582 by Pope Gregory XIII. It corrected the shift of the actual date of the beginning of spring from the Julian calendar and introduced the principle that years with numbers divisible by 100, but not divisible by 400, are not leap years. Therefore, the difference between the calendars is the number of leap years over 400 years. ²⁾

The largest city in Bulgaria is Sofia (1,204,685 inhabitants). The second-largest cities in Bulgaria are Plovdiv (338,153), Varna (334,870), Burgas (200,271), Ruse (149,642). ³⁾

Cyrillic was created in 9th century Bulgaria. Tradition attributes its creation to two saints who converted the Slavs to Christianity - Cyril and Methodius (hence the name of the alphabet). ⁴⁾

The Battle of Varbitza Pass is an armed clash that took place on July 26, 811. The battle is counted as one of the greatest defeats in Byzantine history. The battle was fought by the victorious Bulgarian army led by Khan Krum and the Byzantine army with Emperor Nikephoros. ⁵⁾