This document provides a historical overview of Sofia, Bulgaria, beginning with its origins as a Thracian settlement called Serdica in the 6th century BC. It details Sofia's development under Roman rule and as part of the Byzantine Empire, becoming the capital of Bulgaria in 1879. The summary describes Sofia today as the largest city in Bulgaria with over 1.3 million people and many universities and cultural institutions. It highlights several of Sofia's most prominent architectural landmarks, including St. Alexander Nevsky Cathedral, Ivan Vazov National Theater, and the Vitosha Mountains overlooking the city.