As airfares become cheaper and the world gets more adventurous, India's tourism sector has been reaping the benefits. Revenues are expected to rise by 7.9% over the next decade. In 2012, according to the World Travel and Tourism Council, tourism accounted for 6.6% of India's GDP.

Here's a list of India's most lucrative historical sites, based on the revenues they earned in 2013-2014.

1) Taj Mahal, Agra

Patrick Mcdonald/Flickr
Revenue: Rs. 21,84,88,950

The Taj, Mughal emperor Shah Jahan's marble tribute to his third wife, Mumtaz Mahal, is by far the most iconic structure in India, as well as the country's biggest-earning monument.

2) Qutab Minar complex, Delhi

Saad Akthar
Revenue: Rs 10,16,05,890

The Qutub Minar was built in the early 13th century and is the second-tallest tower in India (after Mohali's Fateh Burj). It is made out of red and buff sandstone and is a UNESCO World Heritage Site.

3) Agra Fort, Agra

Revenue: Rs 10,22,56,790

Agra Fort, another UNESCO World Heritage site, was constructed under the third Mughal emperor Akbar. Some of the great Mughal emperors lived here: Babur, Humayun, Akbar and Jahangir, among others. The country was governed from this fort.

4) Humayun's Tomb, Delhi

Prakash Singh/AFP
Revenue: Rs 7,12,88,110

The tomb of the Mughal emperor Humayun was built in 1572 by his widow, Bega Begum.

5) Red Fort, Delhi

Dennis Jarvis/Flickr
Revenue: Rs 6,15,89,750

The Red Fort served as a palace for Shahjahanabad during the reign of Shah Jahan. The fort derives its name from the red sandstone that is on all eight sides of the structure. It remained a residence for Mughal emperors for 200 years.

6) Group of monuments, Fatehpur Sikri

Wikimedia Commons
Revenue: Rs 5,62,14,640

The "abandoned" city of Fatehpur Sikri was founded in 1569 by the Mughal emperor Akbar. It served as his capital from 1571 until 1585.

7) Group of monuments at Mahabalipuram

Wikimedia Commons
Revenue: Rs 2,72,93,480

The sculpted temples and buildings in this town, 60 kms south of Chennai, are the remains of a port from where ancient Indian traders travelled to Southeast Asia.

8) Sun Temple, Konarak

Damien Roué/Flickr
Revenue: Rs 2,43,52,060

This 13th-century temple in Odisha depicts a solar chariot. The sculpture features 12 pairs of intricately-carved wheels pulled by seven galloping steeds.

9) Group of temples, Khajuraho

Dennis Jarvis/Flickr
Revenue: Rs 2,24,47,030

Khajuraho, in Madhya Pradesh, is synonymous with this large group of medieval Hindu and Jain temples, some of which feature famed erotic sculptures.

10) Ellora Caves

Kirk Kittell/Flickr
Revenue: Rs 2,06,72,820

The Ellora Caves are located 26kms from Aurangabad.  The Kailash temple is one of the largest monolithic structures in the world and resides here.