The immense scope of Sir Thomas Malory¡¦s Le Morte Darthur has long kept daunting his readers. In terms of space, Malory includes both historical locations and imaginary and unnamed natural locales in his work. These places have different functions and therefore transmit different dimensions of spatial imagination. This dissertation examines three kinds of space¡Xwater as space, urban space and mystical space, and the aesthetic relations to these spaces in Le Morte Darthur. These named spaces and the selected locations in each category will be analyzed in the framework of microspace and macrospace, a structure proposed by Dick Harrison in conceptualizing medieval spatial experiences. Chapter one explores water as space. Some geographical sites, such as harbors, lakes, wells and rivers, and an imaginary space of Lancelot¡¦s tears as a qualitative concept are discussed in relation to the aquatic regenerative power. Particular interests are in how Malory accentuates differences which water exhibits in these sites and how water functions as a link to the past and to the future via language and spatial verticality. The second chapter moves to urban space, localized in specific places. This chapter aims to explicate how some medieval cities in Le Morte Darthur are consecrated or deconsecrated as a result of the city¡¦s association with distinct social and moral/immoral activities. The final chapter discusses mystical space. The places of sojourn of the Grail knights during their quest are marked by spatial verticality and horizontality, in proportion to each knight¡¦s moral worthiness. These locales form a preparatory path towards the space where the Grail vision and a divine message are ultimately revealed. An analogy between the interior space of the Grail and the extracosmic void space is drawn in order to convey the essence of the Grail in spatial terms. The progression from chapter one to three reflects a tendency from the physical to the mystical world of the human existence imagined in Malory¡¦s work. Moral dimension plays an important role in that it enables the transformation from microspace to macrospace in some instances. The term ¡§aesthetic spaces¡¨ will include both microspace and macrospace, in which Malory employs real and imaginary sites to fulfill his aesthetic ideal. ¡§Aesthetic spaces,¡¨ when taken in a broader sense, will also apply to ¡§poetic space¡¨ when language results in the transference of space which characters experience. Three categories of texts will be employed in the discussion: literary, historical and theoretical texts. The first group includes Le Morte Darthur, some major medieval English romances and chronicles and the Old French prose Vulgate and Post-Vulgate Cycles; the second, fourteenth- and fifteenth-century philosophical, religious and historical documents; and the last, theories of medieval spatial thinking from Harrison and Mircea Eliade. Through comparisons of a number of passages in Le Morte Darthur and these two French versions, this writer attempts to show that Malory, as the first writer to incorporate the Grail narrative into Arthurian romance in England prior to the late fifteenth century, succeeds in presenting microspatial and macrospatial thinking in Le Morte Darthur.