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Route 5 leads to Saffron City, but it is also the location of the Pokémon Day Care Center.

[edit] Closed Path

You won't be able to go to Saffron City by using the passage house in the south right now - the guard says he's thirsty and won't let you pass. Later on, after you have given another thirsty guard something to drink, you will be able to pass here.

[edit] Day Care Center

Here, you can drop off Pokémon you don't want to carry along, but that you would like to grow nonetheless. You can leave undesirable Pokémon you want to evolve just to complete your Pokédex, or drop off your Magikarp and later on come back to collect a Gyarados. Alas, it's not free. You will be charged 100 for every level your Pokémon gained, but that's a small price to pay for what you get. Keep in mind that every step you travel outside the building gives the bred Pokémon 1 Exp. point, so don't leave a strong Pokémon here.

[edit] Underground Path

The building to the right is the way to an underground path to Route 6. At the entrance, a woman offers to trade a Nidoran male for a female. The underground path is littered with items that travelers accidentally dropped; try searching for them all.