Start the day by visiting the iconic Gateway of India. This Indo-Saracenic arch monument was built in 1924 to commemorate the visit of King George V. Take a boat ride from here to reach the UNESCO World Heritage site, Elephanta Caves. The site has rock-cut Hindu and Buddhist sculptures dating to the 6th and 7th centuries. It is a scenic spot to explore, with stunning landscapes and views of Mumbai harbor.
After the visit to the caves, head to Marine Drive, also known as the Queen's Necklace. This 3.6 km boulevard overlooks the Arabian Sea and is one of Mumbai's most popular spots to hang out with friends or family. Take a leisurely stroll here and watch the sunset. Afterward, head to Chowpatty Beach for some street food such as vada pav and bhel puri.
Begin day two with a visit to the historic Chhatrapati Shivaji Terminus, which is a bustling railway station and a UNESCO World Heritage site. This Victorian building was built in 1887 and is an excellent example of Gothic Revival architecture. Afterward, take a short walk to Crawford Market, one of Mumbai's most famous markets. It sells everything from fresh fruits and vegetables to souvenirs and jewelry.
After shopping at the market, head to the iconic Haji Ali Dargah, a 15th-century mosque and tomb built on a small islet in the Arabian Sea. It is accessible via a narrow pathway that is only accessible during low tide. Afterward, head to Worli Seaface, a coastal promenade that provides stunning views of the Arabian Sea and the Bandra-Worli Sea Link.
If you have more time, consider visiting the Global Vipassana Pagoda, one of the world's largest meditation centers, or the Chor Bazaar, a famous flea market. If you have less time, you can combine Day 1 and Day 2 by spending less time at each location. Do note that some locations might take longer due to travel or waiting time.