The entrance to the Great Pyramid as it appeared before it was barred-up by the Egyptian authorities. In the early part of the 20th century, there were no facilities in the interior parts to assist the tourist in exploring the steep and dangerous passages of the pyramid.
Today there are ramps, lights, handrails, etc.
I would like to quote from an account of the explorations of John and Morton Edgar in 1909. Not only is it fascinating reading, but explains the inner passageways in excellent detail. There is but one original entrance to the interior of the great pyramid. High up the face of the northern flank, and nearly twenty-four feet to the east of the middle line of it, a small doorway leads into the descending passage, which, like all the passages, runs from north to south. A few feet further down the passage we noticed a depression in the roof, into which a rectangular, dark granite block is fitted.