Niš sits 165 kilometers southeast of Sofia, making it Serbia's most accessible Roman city for Bulgarian travelers. The fortress walls enclose 22 hectares of parkland where Constantine the Great was born in 272 CE, and the Skull Tower stands as Europe's most confronting Ottoman monument — a turret embedded with 952 skulls of Serbian rebels from the 1809 uprising against Turkish rule. The journey crosses the Dragoman Pass, where Bulgarian customs gives way to Serbian border posts, and the route descends into the Nišava River valley, where tobacco fields and industrial suburbs frame Serbia's third-largest city. Niš Fortress, rebuilt by the Ottomans in the 18th century atop Roman foundations, remains the city's gravitational center. The main gate opens onto lawns where families picnic beneath plane trees, and the gunpowder magazine now houses a lapidarium of Roman inscriptions. Mediana, three kilometers southeast, preserves mosaic floors and hypocaust heating systems from a 4th-century imperial villa where Constantine's court summered. The peristyle courtyard, reconstructed in the 1980s, reveals the geometric patterns and mythological scenes that decorated triclinium floors. The Skull Tower, built in 1809 on the orders of Hurshid Pasha, originally held 952 skulls arranged in 14 rows — today 58 remain visible behind protective glass. Stevan Sinđelić, the Serbian commander who ignited his gunpowder stores rather than surrender, became the tower's symbolic figure, and the chapel built around the structure in 1892 frames it as a national shrine. Serbian poet Alphonse de Lamartine's 1833 account brought the tower to European attention, describing it as a monument where "the Serbs read their history in the bones of their fathers." Cross-border tours from Sofia bundle visa-free entry for EU and most international passport holders, though travelers should verify current requirements. The 90-kilometer highway transit takes two to three hours depending on border queues, and most itineraries allocate five to six hours in Niš before the return crossing. Guided options include the fortress, Mediana, and Skull Tower admission, while self-drive routes require advance research on Serbian vehicle insurance and green card validity.