The Opera House, completed around 1920, is one of Asmara's most elegant early–20th-century buildings. It's free to have a look around during the resident cafe's opening hours. Or hang around and soak up the atmosphere over a coffee (nfa8; shockingly low quality by Asmara standards) or to use the on-site wi-fi (from nfa20 per hour).
There's no longer a resident opera company in town, but on weekends it's often possible to catch an international football match projected onto the stage's backdrop. Inquire inside for details.