The Land Walls of Constantinople — one of the longest and oldest surviving defence systems in Europe — stretch for 7.2 kilometres along the western edge of the Historical Peninsula of modern-day Istanbul. Built in the early 5th century CE and added to the UNESCO World Heritage List in 1985, this monumental fortification includes the 5.7 km-long Theodosian Walls and the Blachernae Walls, which extend from the Tekfur Palace (Palace of the Porphyrogenitus) to the Golden Horn. For centuries, these formidable barriers protected Constantinople from countless sieges. The walls are pierced by numerous gates — some dating back to the Eastern Roman (Byzantine) era, others added later during Ottoman times.