Agra Fort, Agra (must see)

Agra Fort is a UNESCO World Heritage site located in Agra about 2.5 km northwest of its more famous sister monument, the Taj Mahal. The fort can be more accurately described as a walled city. The 94-acre (380,000 m2) fort has a semicircular plan, its chord lies parallel to the river and its walls are seventy feet high. Double ramparts have massive circular bastions at intervals, with battlements, embrasures, machicolations and string courses. Four gates were provided on its four sides, one Khizri gate opening on to the river. Two of the fort's gates are notable: the "Delhi Gate" and the "Lahore Gate", also known as the "Amar Singh Gate". Because the Indian military (the Parachute Brigade in particular) is still using the northern portion of the Agra Fort, the Delhi Gate cannot be used by the public. Tourists enter via the Amar Singh Gate.

Under Akbar's reign, 1,444,000 builders worked on the fort for eight years, completing it in 1573. The site is very important in terms of architectural history, as some of the most historically interesting mixings of Hindu and Islamic architecture are found here. Agra Fort is one of five wonders for the Indian civilization.

Why You Should Visit:
If you are visiting Taj Mahal, a visit to Agra Fort is complimentary. What a place! It makes Windsor Castle look small.
It's also nowhere near as busy as the Taj and there's more shade so much more pleasant to explore.

Tip:
Take a good guide (the ones inside the fort are nicer/cheaper), and take your time to see and understand in deep all you can get from it.
There's lots of walking, however, so bring good walking shoes, hat, drinking water, and a camera.
Consider going early to avoid most of the crowds.