III. The legacy of Pliska
Geometric and runic-like symbols have been cut into the building blocks,
especially those dating from the pagan period.  Some of the
symbols had been incised at the quarries, when the blocks were hewn, or
immediately before their placing into the walls, because there are symbols found
in their hidden/inner surfaces. Others were put on the frontal surfaces. They
are also found cut into the plates of the sarcophaguses at the Large Basilica,
into clay vessels (prior or after their firing), on items of bone and metal.
Most famous among them is the bronze seven-rayed rosetta from the reservoir. 
Stone block with runic symbols from the village of Bjala, Varna district. VBeshevliev, p. 200
Proto-Bulgarian symbols found on stone elements of constructions. NTjuleshkov, p. 140
30. The symbols know by 1975 were included in the collection of DONCHEVA-PETKOVA L. Znaci vurhu arheologicheski pametnici ot srednovekovna Bulgariya VII-X vek. S., 1980. For a systematisation of the symbols from the imposing buildings together with the newly found examples see: DIMITROV YA. Znaci ot zidovete na monumentalnite postroyki v Pliska. – Pliska-Preslav 6, 1993, p. 69-78.
31. VAKLINOV S. Ein Denkmal runischen Schrittums Pliskas. – Studia in honorem Vesselini Besevliev. Sofia 1978, p. 245-254.