The excavated buildings, despite the destruction, were so impressive, that initially F. Uspenskij thought they were not Bulgarian, but Byzantine. The excavations continued in 1900, when the work on the localities from the previous year was finished and new, partial excavations of the stone fortress and of buildings to the west and to the north of the palace were initiated. A large pagan temple, converted consequently into a church, and two buildings, described as the living quarters of a palace were discovered. The massive stone walls, built of large ashlars, the layout of the buildings as well as the artifacts did not leave space for doubt — this was the capital of Bulgaria from the pagan period.

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http://www.kroraina.com/pliska/index.html - http://www.kroraina.com/pliska/index.html

Tom, their surprise came due to earlier assumptions and inaccurate hypothesis that the ancient Bulgarians were a solely nomadic people who were incapable of building such structures.  They falsely expected to locate only the remains of tent-like materials when examining ancient Bulgarian archeological sites; however, these excavations along with others in the Azov region and in the Volga region (where Kama/Volga Bulgaria was situated, near present day Moscow) proved to those earlier scholars that the old Bulgarians actually built massive, predominantly stone made buildings and other brick/stone structures, where as, tents were mostly used in conquest campaigns within foreign territories.

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