Built in the 17th century, Surb Zoravor Church is one of the oldest standing structures in Yerevan. It is a beautiful church built out of red and black tufa stone (an indigenous building material heavily used in Armenian architecture). Apart from its beautiful stones, many ornamental carvings and khatchkars decorate the Church. Khatchakrs, for those unfamiliar, are traditional cross-stone carvings and they can be found all over historic Armenia.
The church is fairly difficult to spot as it is located in a courtyard and is surrounded by residential buildings. However, it is truly a treasure for those that visit. This is personally one of my favorite spots in Yerevan. Although the church doors close at around 19:00, the small chapel of St. Ananias is open late and visitors can descend a small flight of stairs to visit his tomb.
(P.S. Many medieval churches in Yerevan were demolished by Soviet Authorities. There are only a few standing today.)