请各位英语大神看看这段文字有什么明显的错误吗?

请各位英语大神看看这段文字有什么明显的错误吗?
The biggest Pyramid in Giza is the Khufu Pyramid.It consists of 2.3 million stones and the weight of the pyramid is about 6.84 million tons.It is still a mystery on how they built this great pyramid in such a low level of science.During the process of construction,thousands of workers hauled the huge stones up,and piled them up layer upon layer.It took about 20 years to finish this great construction.