What does it mean to have a transcendent experience, and what does architecture have to do with it? What is ineffable space?Philosphers such as Martin Heidegger and Gaston Bachelard would argue that a true, meaningful human existence can only be found at the threshold between the known, ordered, limited world, and the unknown, chaotic, unlimited world, where the two worlds are one, connected and indistinguishable.The question this thesis poses is what role architecture might play in activating this threshold, in engaging the unknown, in experiencing the sublime.It will investigate this by examining a series of sublime encounters and attempting to express them in architectural form.