Explanation:

- Rani-ki-Vav: This is the correct answer. Rani-ki-Vav, also known as the Queen's Stepwell, is an intricately constructed stepwell situated in the town of Patan, Gujarat. It was built during the 11th century AD and is recognized for its impressive architecture and ornate sculptures.

- Alai Darwaza: This structure is not in Gujarat. It is located in the Qutub Minar complex in Delhi, India. The Alai Darwaza is known for its Indo-Islamic architecture and was constructed by the Delhi Sultanate ruler Alauddin Khalji in 1311 AD.

- Humayun's Tomb: This is a UNESCO World Heritage Site located in Delhi. It is the tomb of the Mughal Emperor Humayun and is an excellent example of Mughal architecture.

- Bibi Ka Maqbara: This structure is found in Aurangabad, Maharashtra. It bears a striking resemblance to the Taj Mahal and was commissioned by Aurangzeb's son, Azam Shah, in memory of his mother, Dilras Banu Begum.