There are many mountains in the world that have a “table top” structure. I will focus on two candidates for the title of the largest flat top mountain in the world.
Mount Roraima: English explorer Sir Walter Raleigh first described this mountain during his expedition to the area in 1596. It is located at a tripoint of three countries: Venezuela/Brazil/Guyana. The mountain’s summit area is defended by 400-metre-tall cliffs on all sides. Its total height is 2,810 m, and its summit surface area is 31km². In short a massive table top mountain.
Here is another view of the top:
Since I posted this answer , there have been many comments about what the top looks like. Here are two photos from World’s Great Wonders by Jheni Osman, that gives readers some inkling what the top looks like:
There is no evidence that pterodactyls or other ancient beast lived on the plateau. Of course the plateau is home to many plant species found nowhere else on Earth. These endemic plants and small animals have developed and are unique to the area.
The second candidate is Table Mountain, Cape Town, South Africa: The table top is 1,086 metres (3,563 ft) above sea level. The length of the “ table” is approximately three kilometres (2 miles). The pic below is the front view as seen from the waterfront area of Cape Town.
Table Mountain is certainly not as high as Mount Roraima, and as far as I can tell from my visits the “flat top” does not exceeds 31 square kilometers. Thus Mount Roraima takes the prize as the largest table top mountain.
But what is clear is that anyone can readily get to the top of Table Mountain via cable car, or you can hike up, which I have done. Here is part of the Smuts trail that starts in Kirstenbosch Gardens that I took:
It takes about 1.5–2hrs to reach the top.
In contrast to get to the top of Mount Roraima requires serious climbing with professionals.
The view from the top of Table Mountain is spectacular. Here is a view from the Top of Table Mountain, with Cape Point in the distance. Note the dam/reservoir on the top of Table Mountain. This pic was taken near Maclear's beacon, the highest point on Table Mountain
Our hike started in Kirstenbosch Gardens following the Smuts trail. Here is a view of Cape Town and Signal Hill from the Top:
And finally a view of Camps Bay on the Atlantic side
So in summary Mount Roraima is the largest flat top mountain the world based on height and the expanse of its table top, but Table Mountain though second in size and height can be readily experienced by all, either by hiking or taking the cable car to the top!