須彌山北魏洞窟的空間佈局及其宗教功能：以第22、24窟為例的考察=The Spatial Arrangement and Religious Functions of the Xumishan Grottos of the Northern Wei Dynasty [386-534]: The Case of Caves 22 and 24
Caves 22 and 24 were created during the Northern Wei Dynasty (386–534) and were the earliest caves with the central pillar structure (Ch. zhongxin zhu 中心柱). Central pillar is a sinicized Indian stūpa, which not only serves as an alter for relics or a symbol of Buddha, but also functions as a stūpa that a visitor could circumambulate clock-wise. All four walls in the grotto have no mural, perhaps in order to highlight the function of the central pillar as the stūpa. The central pillar has three layers and, on all four sides, has the imagery of Four Marks that show the enlightening process of Buddha Śākyamuni, as well as Four-Direction Buddhas and Thousand Buddhas, which all serve as the objects for meditation. Even though the imageries vary in themes, they are all related to the visualization practice during the meditation. In short, the grotto bespeaks a deliberate spatial arrangement.
