Where is Middle-Earth?

This is a topic that really interests me - its been covered a little, if i've missed a good posting on the subject sorry and please redirect me.

where is middle earth? it could be said that its completely fictious and has no roots in reality, but i think not. i dont think tolkien was ever 'copying' from history, but he certainly had a sense of geography and history.

1. the shire. from its name and description i think its almost certainly based on england, more specifically the agricultural south where tolkien grew up. the hobbits represent the simple country people tolkien knew.

2. the dwarfs. the dwarfs seem to have strong norse influences in writing and culture.

3. the elves. could the elves represent the celts? im not really sure on this one, but they seem like the celts - mysterious and magical but receding in numbers and migrating to the west.

4. mordor and gondor. by the way they are positioned, mordor/gondor look a lot like turkey/byzantine empire. from c.1000 to c.1500 there was an epic struggle between the ottoman empire (turkey) and the byzantine (or eastern roman) empire. the byzantines were waning in strength, and eventually just constantinople (their capital city) was left, acting as the only defence against turkey. this seems very much like minas tirith vs. mordor, and many saw it as a struggle of (christian) good against (islamic) evil.

well its mainly conjecture on my part and probably wrong, but please tell me what u think the explanation of middle earth is