The document provides information about three notable Islamic structures:
1) Humayun's Tomb in Delhi, known for being the first Mughal structure to use red sandstone and for establishing the garden tomb typology. It has a symmetrical nine-fold plan centered around a domed chamber.
2) The Red Fort in Delhi, built in the mid-1600s, which served as the main residence of the Mughal emperors. It has various palaces and gardens within its fortified walls.
3) The Red Fort in Agra, constructed in the late 1500s, which also housed Mughal emperors and features buildings like the Jahangir Palace and Sheesh Mahal