Varna's main cathedral was built between 1880 and 1886, just a few years after Bulgaria gained independence from the Ottoman Empire. The timing matters: the cathedral is a statement of restored Orthodox identity as much as it is a place of worship. It sits in a central square near the pedestrian zone, its yellow-ochre facade and copper domes visible from much of the surrounding area.
The interior is richly decorated with icons and frescoes, and the cathedral's atmosphere is genuinely devotional rather than tourist-oriented — services are held regularly and the building is used as an active church. The iconostasis is particularly fine. Worth a short visit even if Orthodox church interiors aren't usually your thing; the light in the late afternoon is particularly good.