Built in 1193 Qutab-ud-din Aibak wanted Qutab Minar to be to a formidable monument to commemorate the advent of the Delhi Sultanate over the last Hindu kingdom.
More than 8 centuries later , with 73 meters high, Qutab Minar still is the tallest stone tower built in India.
A later sultan of Delhi, Ala-ud-din Khilji (1296-1316 AD) wanted to change this. Buoyant by his recent conquest of the south Indian kingdoms, Ala-ud-din Khilji wanted to make a memorial tower, twice as tall as the Qutab Minar. He made the master plan and set the foundation. But the construction could not go more than a floor at 24.5 meters by the time of his death.
Unlike Qutab-ud-din Aibak's successor who completed the work of Qutab Minar, Ala-ud-din Khilji's successors could not pursue the work of Alai Minar.
The Alai Minar looks like an an abandoned rubble structure. But it gives great insights into the architectural techniques and design that went into the those structures. The dressed exterior stones are missing, but it still reflects the decorative fluted outer walls , more sophisticated than the Qutab Minar.
You can also see a few windows on this unfinished tower.