The first day of the trip, head to Fort Aguada, a 17th-century Portugese fort located on Sinquerim beach. The fort was built to defend against the Dutch and Marathas and has many interesting architectural features. Go for a walk around the fort and enjoy the scenic views of the Arabian sea. The lighthouse was renovated recently, which is now open to the public and offers a beautiful bird's eye view of the sea and adjoining areas.
On the second day, visit one of the most popular beaches, Baga beach, known for its lively nightlife. There are plenty of watersports to try, or you can enjoy some shopping or live music on the beach from the vendors. Go to Britto's Bar & Restaurant for lunch to try some authentic Goan cuisine.
On the third day, head to the beautiful Dudhsagar waterfalls, known for its milky white cascading water during the monsoon season. The waterfall is located inside Bhagwan Mahaveer Wildlife sanctuary. You can reach the waterfall by either trekking or taking a jeep safari.
On the last day, visit Ancestral Goa, also known as "Big Foot Goa," a museum that showcases Goa's cultural heritage. The museum has a replica of a Goan village and gives hands-on experience of traditional Goan life. Near the museum, visit the Mangueshi temple, known for its unique architecture. You can shop for some souvenirs in the Panaji market and end the day with some street food.
If you have more time, try to visit some more beaches such as Calangute or Anjuna. Or, you can try some water activities like scuba diving, windsurfing or parasailing. If you have less time, you can skip Dudhsagar waterfalls or Ancestral Goa museum, depending on your preference.