Simply put, Karnak is the largest temple ever built in the history of the human race. The sheer size of the temple will astound virtually anybody. However, it needs to be recognized that what we see today as the Karnak temple is the result of 1,300 years of building on the temple grounds.
Karnak is actually a complex of three separate temples built for three different gods: Amun, Mut, and Montu. The most impressive part of the the temple complex is the Hypostyle Hall. This shows up soon after entering through the main doors and then passing through the Second Pylon. This hall is comprised of 7 rows of columns that are 42 feet high. Each row contains 9 columns apiece. Standing in the center of it and looking up makes you feel like Gulliver in the land of Giants. Just this one hall, which is a small part of the Karnak complex, is bigger than several of the large cathedrals in Europe combined. Along many of the walls around Karnak are hieroglyphs depicting scenes of politics, war, and religion with the appropriate pharaohs who had them built during their reigns. There are a number of smaller temple buildings scattered around the complex dedicated to many other gods than the three main ones. There is also a large lake on the grounds that was believed to be sacred and is called the Sacred Lake. This is a sight that is not to be missed.
We actually went to Karnak twice, once for the tour itself and then again for the laser and light show at night. Although the laser show was interesting, the one at the Great Pyramid in Giza was far better. I actually enjoyed touring the temple complex during the day much better. I was able to take in the sheer magnitude of the temple while at the same time marvel at the details carved on the reliefs throughout the complex.
From journal The Sands of Time