The hereafter following is abstract of the discourse held by Prof. dr. ir. C. L. Temminck Groll in honour of the jubilee 1899-1989 of the KNOB on September 23th 1989. The KNOB (Royal Antiquarian Society of the Netherlands) exists 90 years. A respectable age after human standards. Although a society depends on human devotion it does not know age limitations. This is an excellent moment to reflect upon our centenary. Then, in 1999, we will have to present an extremely good manifest for the coming millennium! We have been spoiled very much during the past 90 years. Which of the founders would have expected so many people professionally involved at the protection of monuments? Which of them could have estimated the money available to realize re...