The height of the dome of St. Peters Basilica is 448 feet (136.5 meters). The next tallest is Big Ben Clock Tower which stands 315 feet (96 meters). Third is the US Capitol which has a height of 289 feet (88 meters) for it's dome. Finally, the fourth tallest structure of the choices is the Taj Mahal at 213 feet (64.9 meters).

These structures do not compete in any way related to purpose, use or history. Each has it's own unique place in the culture of the world and each is worthy of a visit where we stand, look at their height, and reflect on the "engineering" remembering the time period in which each was built.

More Info: en.wikipedia.org