Hampi was the capital of Vijayanagara Empire from the 14th century to the empire's downfall in 1565. At 1500 CE, Hampi was the second largest city in the world. Today, Hampi is a beautiful set of 1600 ruins sprawled out over 16 square miles. Hampi is not yet flooded with tourists. It's not undiscovered but the hoards of tourists that mob a world famous site like Angkor Wat are not present, at least yet.
Walking among the ruins, one imagines Hampi's glorious past when it was the capital of a rich and prosperous empire. The highlight of Hampi is the Vittala Temple with its famous stone chariot and ornately carved structures. Wandering through the paths and seeing the many only partially reconstructed structures was a delight.
If you are interested in Hampi, I would go sooner than later. It's a world class set of ruins. I suspect that overtime, there will be more and more visitors. Today, it's 6 to 7 hour road trip from Bangalore. However, there's much road construction underway and the drive time will drop. As Hampi becomes better known and easier to get to, I can see it becoming much more crowded with tourists.