For a quarter of a century we have been engaged in a systematic examination of high-quality photographic (optical) sky surveys in the search for new celestial bodies of various kinds. It took about 5000 hours to cover the whole northern celestial hemisphere and half of the southern one. In total, about 12000 new objects were discovered. From the very beginning of our programme we also searched for objects (or groupings of them) of rather peculiar morphology. The motivation was to detect objects revealing exceptional physical processes, on the one hand, but also to discover constructions possibly created by advanced extraterrestrial civilizations (ETCs), on the other hand. A number of very peculiar objects were indeed found (these were mostly studied in detail later), but none of these appeared likely to be the product of alien masterminds. We may conclude that at least within about 10000–20000 light-years around the Solar system no highly advanced ETCs intend to reveal themselves through such objects.