20190521_Bulgaria_6473 Sofia sRGB
In the courtyard behind the Presidency (the Bulgarian president’s office) are Roman ruins from the 2nd century CE. Beyond them is the oldest building in Sofia, the Rotunda of Sveti Georgi (Saint George) built by the Romans in the early 4th century CE. It was used as a church starting in the 6th century CE. In the 16th century CE it was converted into a mosque by the Ottomans until being abandoned when Bulgaria was liberated in 1878 CE. The building was restored starting in 1915 CE and is a functioning Eastern Orthodox church today.
Bulgaria was settled by Thracians (by the 12 century BCE) who were conquered by the Persians (6th century BCE) but later regained control (5th century BCE). The Macedonians took over (4th century BCE) until succumbing to the Celts (3rd century BCE) before the Roman Empire annexed Thrace in 45 CE. The Bulgars invaded and signed a peace treaty with the Byzantine Empire [Eastern Roman Empire] in 681 CE to launch the First Bulgarian Empire. In 1018 CE the Byzantines seized back control until an uprising in 1185 CE led by Asen dynasty nobles initiated the Second Bulgarian Empire. By 1396 CE, following more than a decade of attacks, the Ottomans had enserfed the Bulgarian people who gradually supplanted their ethnic identity with a religious one, Orthodox Christianity. In 1877 CE, the Russians declared war on the Ottomans who were defeated with the aid of Bulgarian rebels. The treaty signed on 3 March 1878 CE called for an autonomous Bulgarian principality, establishing the Third (current) Bulgarian State. [March 3 is the National Liberation Day holiday today.] In 1944 CE monarch (tsar) rule was abolished. In 1946 CE, Bulgaria became a socialist state ruled by the Communist Party until a revolution in 1989 CE transformed Bulgaria into a democracy.
On Google Earth:
Rotunda of Sveti Georgi 42°41'48.96"N, 23°19'22.42"E
Presidency 42°41'48.56"N, 23°19'25.86"E