This paper discusses the outline and the background of the phenomenon named "merged temple" (Photo 1, Fig. 1), a composite building occurred by extension of 'sub-building' covering or wrapping an existing Hindu temple, or 'main-temple', frequently observed in the Old City of Varanasi (Uttar Pradesh, India), revealing their number and distribution, morphological variations, forming process and condition, and so on, through field survey and interviews with residents (Table 3). The main points of argument and the findings can be summarized as follows.<br><br> (1) Based on the past researches, the authors pointed that Hindu temple has three characteristics, that is, the continuity (temple continues to be as temple), the immobility (temple rooted in the place cannot be moved), the variability (temple building can change its form as necessary while allowing secular uses).<br> (2) Reviewing the basic information about temple in Varanasi, it was confirmed that numerous temples have been densely amassed in the old city, most of temples are privately owned, and that shikhara and its finial are symbolically quite important elements of temple building (Photo 3, Fig. 3).<br> (3) "Merged temple" is defined as a permanent composite building with internal space that occurred as the result of the extension or new construction of the adjascent building covering or wrapping an existing Hindu temple originally built independently (Fig. 4).<br> (4) Setting the criteria of merged temple, the authors revealed its number and distribution tendency by field survey, and indicated its presence in the urban space. Approximately 38% of temples in the surveyed area are merged temples and they are found somewhat more in the area early urbanized (Fig. 2, Table 1).<br> (5) Eight morphological types of merged temple were shown based on the degree of horizontal overlapping and the covering of the finial (Fig. 5, 6). Those morphological variations seem to be generated through the competition of two forces, one oriented respecting the existence of main-temple and the other oriented increasing the space of sub-building.<br> (6) Most of sub-buildings of merged temples are residences where their owner's family lives. Main-temple and sub-buildings are owned and sold together. While residents are often non-Brahmin, they perform daily puja and management of the main temple.<br> (7) The function of main-temple always remains, and the access to main-temple is almost consciously opened for neighbor devotees or pilgrims even in the case that main-temple is completely wrapped within sub-building.<br> (8) Merged temples have occurred mainly since the late 20th century. Many of them seem to have been secondarily formed through a series of extension of the sub-buildings motivated to increase their floor area.<br> (9) Residents are strongly conscious the norm prohibiting destruction and relocation of temples. While there is a possibility that temple may be demolished with the intention of the owner, its survival is regarded as a public issue to some extent.<br> (10) Although the norm that prohibit covering temple with building are shared among residents, its content has a range of interpretation and it appears as different architectural correspondences.<br> (11) Based on the above findings, the authors discussed that merged temples of various shape and degree are generated as a result of the interacting of the extrinsic development pressure and the intrinsic characteristics of Hindu temple, the continuity and the immobility, in the urban space historically amassing numerous temples. There the moderate plasticity of temple building, which is secondarily sacred, works effectively as a medium (Fig. 7).