Somewhere in London, probably disguised as a British police box. Better question might be "when" is your time machine.
Where is my honky-tonk piano?
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It is easy to go down into Hell;
Night and day, the gates of dark Death stand wide;
But to climb back again, to retrace one's steps to the upper air –
There's the rub, the task.
– Virgil, The Aeneid (Book VI)