Agios Nikolaos is a beautiful seaside town in Crete, popular among tourists for its beaches and mild climate all year long. There are plenty of things to do in Agios Nikolaos and the surrounding area, including:

1. Lake Voulismeni: This is a small lake in the center of town, surrounded by restaurants and rocky cliffs. You can stroll around the lake, feed the ducks, or enjoy a meal at one of the many waterfront restaurants.

2. Beaches: Agios Nikolaos has several beaches, including Voulisma Beach and Almyros Beach, where you can catch some rays and swim in the clear blue waters.

3. Panagias Keras Church: This is a beautiful church located on a hill overlooking the town. You can climb up to the church for stunning views of the surrounding area.

4. Cretan Olive Oil Farm: This is a great place to learn about the production of olive oil and taste some of the best olive oil in Crete.

5. Boat Trips: You can take a boat trip to Spinalonga Island, a small island near Elunda that used to be a sanctuary for people with leprosy, or to Balos Lagoon and Gramvousa, two beautiful locations with crystal-clear waters.

6. Nightlife: Agios Nikolaos has a vibrant nightlife, with many shops and restaurants open into the evening. You can take a stroll around the lake, past the restaurants, and beyond to the lit shrine at the back of the lake. Alternatively, walk along the port, out around the town, and enjoy the lively atmosphere.

7. Sightseeing: You can explore the town on foot, visit hidden churches, and admire the tree-lined pedestrian streets. You can also take day trips to nearby attractions, such as olive farms, abandoned castles, and rural villages.

As a general rule, four days in Agios Nikolaos is a good time to see a bit of everything in and out of the city.