In the northeast part of Route 209, you find Lost Tower, where you can climb to the top while battling trainers and finding items.

Catch Pokémon

On the first floor of Lost Tower, you can catch Gastly, Misdreavus (Shining Pearl only), Murkrow (Brilliant Diamond only), and Zubat.

Go up the stairs.

Lost Tower 2F

If you go west, you can battle Youngster Oliver, who has a level 16 Stunky, a level 16 Kricketune, and a level 16 Shellos. You get 512 Pokédollars for winning.

North of the Youngster, there is an Oval Stone.

Go west, then north and up the stairs.

Lost Tower 3F

In addition to the other pokémon that you can catch in Lost Tower, there is a small chance of encountering Golbat on floor 3F and higher.

Go south, then west, and you can battle Roughneck Kirby, who has a level 19 Cleffa. You get 684 Pokédollars for winning.

Go west to find a Revive.

To the north, you can battle Poké Fan Leonard, who has two level 15 Pichu and a level 18 Pikachu. You get 1440 Pokédollars for winning.

Go up the stairs.

Lost Tower 4F

Southwest of the stairs, there is a hidden Great Ball.

If you go toward the southeast corner of the area, you can battle Poké Fan Rebekah, who has a level 19 Bonsly. You get 1444 Pokédollars for winning.

South of that, you can battle Ranchers Beth and Bob. They have a level 19 Buizel and a level 19 Ponyta. You get 4712 Pokédollars for winning.

To the west, there is a TM27 Low Sweep.

North of that, you can battle Young Couple Nat and Mike, who have a level 19 Murkrow and a level 19 Misdreavus. You get 5320 Pokédollars for winning.

Go up the stairs.

Lost Tower 5F

Talk to the person on the right to get a Cleanse Tag. Talk to the person on the left to get some TM96s, which teach Strength. You will need a badge from one of the Gyms before you can use it in the field.