The northern wall of the cathedral contains two reliefs which depict Paul the Apostle and Saint Thecla and a cross with all arms of equal length with Greek inscriptions. Paul and Thecla are represented in conversation, Paul is shown seated on cross-legged stool. These reliefs have been dated by various authors between the first and sixth centuries. Shahkhatunian and Ghevont Alishan suggested that these reliefs were created before the invention of the Armenian alphabet in 405. Art historian Sirarpie Der Nersessian believed that they are from the fifth or sixth century. In his 2012 analysis, Grigoryan wrote that "we can insist that the three reliefs of the Echmiadzin Cathedral were created from the very beginning, in 302–325." According to Hasratyan they are the earliest reliefs on the cathedral's walls and among the earliest items of Christian Armenian sculpture art.