Question: Where is Āmítuófó’s (阿弥陀佛: Amitā[bha] Buddha) Pure Land (净土)?
Answer: The brief answer is in this teaching by Śākyamuni Buddha (释加牟尼佛) in the Amitābha Sūtra《阿弥陀经》.
From here, [in the] western direction, passing a hundred thousand koṭis [of] Buddha Lands, is [a] world named ‘Ultimate Bliss’. [In] that land, is [a] Buddha named Amitā[bha/yus, who is] now speaking [the] Dharma.
More detailed notes on these two lines are as below.
 ‘Here’ refers to the ‘Sahā World’ (娑婆世界), which is the galactic system (i.e. galaxy 星系; world system), the Milky Way (银河系) we are in.
 With 1 koṭi (亿) being 10 million, ‘a hundred thousand koṭis of Buddha Lands’ (十万亿佛土) refers to 1 trillion galaxies where there are Buddhas teaching. These Buddha Lands can refer to world systems which are defiled lands (秽土) and pure lands.
 The other Pure Lands can be similar to Āmítuófó’s Pure Land, functioning as skilful exits of the three realms of desire, form and formlessness (三界：欲界，色界，无色界).
 The vast physical distance between here and Āmítuófó’s Pure Land expresses great spiritual estrangement (or alienation), that can nevertheless be covered swiftly by connecting to Āmítuófó sincerely by mindfulness of his name, to be received and guided by him.
 Being stated to be ‘in the western direction’ (西方) ‘from here’ (从是) means Āmítuófó’s Pure Land is in a physically tangible and exact position with reference to the Sahā World. Even in an expanding universe, this relative direction is constant.
 The ‘two “is“‘ (二有) in ‘is a world (有世界)’ and ‘is a Buddha (有佛)’ are double affirmations of a physical Buddha in his physical Pure Land. Both are thus material yet pure; not merely mind-only (唯心). Āmítuófó’s Pure Land is also described to be with the most refined materials, which function as the most skilful Dharma teaching aids.
 If Āmítuófó’s Pure Land is situated totally inside the three realms, there would not be adequate outstanding spiritual advantages to be born there, or guarantee that it will lead to the complete enlightenment that Āmítuófó attained, with which he shaped his Pure Land.
 Āmítuófó’s Pure Land’s forms, situated totally outside the three realms, are not the usual forms here, which would make it a worldly ‘land’. However, birth in it is not equated to instant enlightenment, as there is still learning and practice needed in Pure Land, albeit being the swiftest with its pure forms and means. If it is entirely outside the three realms, with no connection to them at all, there would be no need for the Buddha to point out its specific direction, to give us a sense of direction. However, just as the main exit in a building is in one fixed location, that can be accessed by those inside, Āmítuófó’s Pure Land is situated as stated by the Buddha.
 Āmítuófó’s Pure Land can be depicted in part to function like a ‘bridge’ to receive beings from inside the three realms, to be guided to outside the three realms. This does not mean it has to be at some physical border of the universe, but that wherever his Pure Land is physically, it is definitely at the spiritual border between being in and out of the three realms, that can be reached instantly with connection to Āmítuófó’s blessings. Since having reached it attains non-retrogressive progress to Buddhahood for sure, being born in his Pure Land is often directly described as to exit the three realms (出三界).
 Being inconceivable (不可思议), Āmítuófó’s Pure Land might be an extraordinarily large and special galactic system, that can expand at will to accommodate as many beings as needed with his immeasurable meritorious virtues, (and with its beings’ also collective immeasurable meritorious virtues), or an alternative kind of world system, that transcends the limited understanding we have with our unenlightened minds. It is a ‘World [Of] Ultimate Bliss’ (极乐世界), with ultimate spiritual and physical peace and bliss (安乐) of body and mind possible, for both the unenlightened and the enlightened, culminating in the truly ultimate bliss of Buddhahood.
Extra Note: Interestingly, as taught by the Pure Land Tradition’s 9th Patriarch Great Master Ǒuyì (净土宗九祖蕅益大师) in ‘Essential Explanation [Of The] Sūtra [In Which The] Buddha Speaks [Of] Amitā Buddha’《佛说阿弥陀经要解》below, the above two lines introduce the Three Provisions (三资粮) of Faith (信), Aspiration (愿) and Practice (行) for reaching Āmítuófó’s Pure Land.
… [The] two ‘is’ [and] ‘now’, [is this sūtra’s] preface [for] urging Faith. ‘World named’ [as] ‘Ultimate Bliss’, [is the] preface [for] urging Aspiration. ‘Buddha named “Āmítuó[fó]”‘, [is the] preface [for] urging [the] wonderful Practice [of] upholding [his name].
Verse On Faith, Aspiration & Practice
[Have] Faith [that there] is [Amitā(bha)] Buddha in [his] Pure Land,
[have] Aspiration [to be] born [in his] Land [Of] Ultimate Bliss,
[have] Practice [of] mindfulness [of] Āmítuófó[‘s name],
[and the] Three Provisions [are] immediately complete.
Is Āmítuófó’s Pure Land Physically Far To The West?
Is Pure Land Only In The Here & Now?
How Pure Lands Transcend The Three Realms
 Immeasurable Life Sūtra’s Thirtieth Chapter’s Summary & Explanation
Śākyamuni Buddha’s Pure Land On Spirit Vulture Mountain (And Related Pure Land Concepts)