You needn't have a strong religious faith to enjoy the serene atmosphere of Sourp Krikor Lusavorich Cathedral. Inquire when the next mass starts or when it's open for general viewing.
This principal church in Kentron comes recommended by fellow travelers, so make a spot for it on your travel itinerary. However, your day doesn't end there. There are a lot more attractions waiting for you to appreciate after Saint Gregory the Illuminator Cathedral. Republic Square, Yerevan Cascade, and Yerevan Opera Theatre are not far away.