Located beyond the fringes of Pinwheel Forest, Nacrene City used to be the home of the Unova region's second gym. Those duties have since been passed off to Cheren in Aspertia City, turning Nacrene City into just another stop on your post-game journey. There's still plenty to see before you move on, however.
- Right beside the road is the Café Warehouse. Speak to the woman running behind the counter on Wednesdays to receive a free Soda Pop, or on Saturdays to receive a free Lemonade. If you speak to the waitress who appears on the lower levels on Sunday she'll give you a Grubby Hanky, which you can give to a man on Thursday. Tell the waitress on the next Sunday to receive a Fluffy Tail.
- East of the Café Warehouse is the Museum. Step inside and the assistant director will offer to give you a tour, only to be interrupted by a mystery woman. She'll offer you either the Cover Fossil or the Plume Fossil. You can then give the Fossil you chose to the woman at the desk on the right to receive either a Tirtouga (Cover Fossil) or an Archen (Plume Fossil). You'll need to make space in your team to accept the Pokémon. You can use this desk to restore Fossils from Twist Mountain, as well.
- In the southeast of Nacrene City is a shop that deals in Décor items. You can only use Décor as part of the Dream World feature, an online segment of fifth-generation Pokémon games that was shut down in 2014. So. Move on.
- Check the house to the west of the Pokémon Center with the stairs on one side. Inside the home is a Move Tutor who wants Green Shards. Most of the moves he teaches require an advanced knowledge of combat to use effectively, and are quite dangerous in the right hands.
- Follow the train tracks in the southwest of Nacrene City. You'll hit a dead end that you probably spotted while exploring Pinwheel Forest. There's a hidden PP Up at the end of the tracks.
In addition to all of the above, it is possible to run into Uxie, a legendary Pokémon, in Nacrene City. If you've been to the Cave of Being on Route 20 since becoming the Champion you'll know that Uxie, Mesprit, and Azelf are loose in Unova. Approach the Museum entrance from the south and you'll receive a little notification that there's a presence. Choose to encounter it and Uxie will appear to battle you.
That's all for Nacrene City. You can proceed through the gate in the southeast to Route 3. Here you'll find a Breeder who has an Egg she wishes to give to you. Make space in your party and accept. If you choose to hatch the Egg by walking it you'll receive a Happiny. Nice! Onward to Route 3!