A phenomenon of large-scale solar activity - relatively weak extended emitting chains with a characteristic length comparable with the solar disk radius or even diameter - were detected recently on the modified heliograms in the microwave (Nobeyama radioheliograph), soft X-ray (Yohkoh/SXT), EUV (SOHO/EIT, TRACE), and some other ranges. In this paper, some examples of the chains are presented to draw attention to their existence. Evidence on the reality of the chains is given, particularly based on the following factors: (a) the coincidence of the chains with other large-scale structures, particularly with boundaries of some coronal holes; (b) the similarity and identity of the clearly distinguishable chain-like structures on the various spacecraft and ground-based heliograms at different wavelengths, and (c) intensity changes of the chains of long duration ranging from a few tens of hours to several days. Some features of the long-lived and transient chains, including their relations to long-duration events (LDEs) and coronal mass ejections (CMEs), are outlined briefly. Based on the observed properties of the chains it is suggested that at least some of the chains are visible manifestations of separators or quasi-separatrix layers formed between different interacting large-scale magnetic flux systems in the evolving global magnetic solar atmosphere. In this paper, some images and movies illustrating the chains are presented also on the accompanying CD-ROM.