What's sad to me is that so few people get to see the ruins because of the demon spawn Robert Mugabe! (But let's not go into politics now...

)
But it mustn't be left out of the equation...
1. One of the reason why some people - archaeologists and historians - don't believe the ruins to have "African" origin, is because it's not
typical "African". The African tribes from that era and area didn't build stone structures. The hunter tribes built wood and straw huts that
didn't require much time and effort, because they were nomads. The farmer tribes built clay/mud huts. But there is no reason why any African tribe
couldn't put two rocks on each other and realize that they could build a stone structure which would be stronger. (Tribal wars were common in those
times.)
2. What little evidence exists suggests that Great Zimbabwe also became a centre for trading, with artefacts suggesting that the city formed part of a
trade network extending as far as China. Chinese pottery shards, coins from Arabia, glass beads and other non-local items have been excavated at
Zimbabwe. This would point to the European explorers and trading routes of that time.
3. There is a legend going round that the structures were built to replicate the palace of the Queen of Sheba in Jerusalem. Now the dating (of the
site and the theoretical era of Sheba) indicates that this theory is a bit of a stretch.
4. There is reason to believe that Archaeologist withheld (and perhaps) destroyed some of the information that may give clues as to who exactly built
the ruins. This is the part where politics comes into play, and also a very important note. According to Paul Sinclair, interviewed for None But
Ourselves (1982):
I was the archaeologist stationed at Great Zimbabwe. I was told by the then-director of the Museums and Monuments organization to be extremely careful
about talking to the press about the origins of the Zimbabwe state. I was told that the museum service was in a difficult situation, that the
government was pressurizing them to withhold the correct information. Censorship of guidebooks, museum displays, school textbooks, radio programmes,
newspapers and films was a daily occurrence. Once a member of the Museum Board of Trustees threatened me with losing my job if I said publicly that
blacks had built Zimbabwe. He said it was okay to say the yellow people had built it, but I wasn't allowed to mention radio carbon dates... It was
the first time since Germany in the thirties that archaeology has been so directly censored.
5. An even more important indication that it was probably built by native Africans is the Khame Ruins - also in the Zimbabwean country.
Khame (also written as Kame or Kami) was the capital of the Torwa State that emerged as a strong power in south-western Zimbabwe after the decline
of Great Zimbabwe in the 15th Century. In the late 17th Century the site was burned and levelled by the Rozwi, who then took it over. In the 1830s
Nguni speaking Ndebele raiders displaced them from Khame and many of the other sites they had established.
Source
There is no question that native Africans built Khame, and lived there. It strongly resembles the Great Zimbabwe ruins. (Some may suggest that the
Rozwi "copied" the Great Zimbabwe ruins, as there are many architectural differences, but the decorations suggest the same cultural background.)
See also:
More Information
Pictures
I hope Zimbabwe's BS gets sorted out, because it's a tourist goldmine, but Mr Mugabe is keeping the rest of the world from seeing it's great
historical and natural treasures.