Angular view of the top part of an Obelisk at the Karnak temple in Luxor

The Obelisk is a truly fascinating structure. It looks pretty impressive, having been fashioned from a large piece of stone in quarries (through an elaborate system where water is frozen,expands and breaks the rock; and then the Obelisk is sent on river barges to the site of the temple).
Inside the Karnak temple, this is just the top part of the Obelisk, put on some supports and kept in such a way that the magnificence of the structure is clearly visible to all tourists.
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Collapsed structures against the backdrop of a crane at the Karnak temple in Luxor

When you have an ancient structure such as the Karnak temple in Luxor (built approximately 35 centuries back), there is the chance of tremendous wear and tear, and damage to the structure over the centuries (consider that at another site, the Colossi of Memnon, the entire temple has vanished over the centuries).
In this photo, you see how much of the structure has actually been damaged, with the stone blocks that make the walls of the temple lying around, and broken.
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Some of the more damaged structures inside the Karnak temple in Luxor

In many of the previous photos, you would have seen some great examples of items inside the Karnak temple that are wonderfully preserved even though there have been 35 centuries since the temple was made. Many of the structures that are seen as preserved have been actually restored. However, this photo shows a section of the temple where the structure has seen the wear and tear of the centuries gone past, and where the wall has broken. You can still see some of the carvings on the walls, but the overall impression is that of strong wear and tear.
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Some amount of degraded walls at the Karnak temple in Luxor

The problems with historical structures is that the urge to preserve them (along with the financing and the technology) has only happened in the last few decades. For many historic monuments, the damage over the centuries to parts of their construction (or in some cases, to the whole monument itself) is so considerable that they cannot be restored. This wall where the structure seems so badly damaged is an example where there was no need to try and restore it.
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