You'll probably see Dormition of theotokos Cathedral from a distance before you actually find this grand place of worship. Step inside if the doors are open or just appreciate the facade from outside.
If you're staying a while in Old Town Cluj-Napoca, Dormition of theotokos Cathedral is a good place to kick off your exploring. This principal church is one of numerous attractions worth seeing here. Unirii Square, Avram Iancu Square, and St. Michael's Church are also waiting for you nearby.