The Museum[edit]
In this chapter, you'll be playing as a young Nathan Drake. Head into the museum and you'll get a tip: press 
to look at Drake's journal. You should see an exhibit with some cannons when you first enter. Look in one of the cannons to find an 003Emerald and Diamond Ring. When you find nothing on the first floor, head for the stairs (you might want to look to the right of the staircase first - there should be an 004Antique Coin Purse behind a vase). There should be a case in the middle of the room with some of Francis Drake's possessions. Look at all of the display cases for a trophy, then examine that case for a cutscene in which Drake is thrown out of the museum. Now you'll have to follow Sully.
Following Sully[edit]
Go to the sidewalk on the right under the building next to the blue car. By a door you should find a 005Antique Colombian Soup Ladle. Follow Sully around the corner, then take cover behind the car with 
. Follow what the onscreen prompts tell you to do until you reach the end of the fruit stand. After Nate eats the rotten fruit, keep following Sully. He'll go into a meat market. Stray from the path a bit and head to a stand with jars on it (across from a long staircase) to find a 006Pottery Chimu Vessel. Don't follow Sully into the meat market just yet. Another treasure can be found when following the street to a gate (a dead end) and, at the top of a staircase across from Cafe El Sol, you should find a 007Ancient Chupicuaro Figure. Now follow Sully into the meat market and keep following him until he goes behind a locked door.
Jump onto the ledges surrounding the door, then keep going left on the next ledge until you can jump up onto a window ledge. Jump from the air conditioner to the next window ledge, then jump onto the next air conditioner and take the next window ledge up to a yellow pipe. Climb to the bars, then swing to the windows where you'll be able to get a good look at the scene. After the cutscene, jump to the railing by the window to the right, then jump on the yellow pipe again. It'll dislodge from the wall and you'll have to swing to the balcony. Get the 008Shamanistic Jaguar Head at the end of the balcony, then climb onto the roof of a building by swinging from the sign, shimmying on the ledge, and jumping across to the roof of a building. Next, jump onto the hotel sign (after Sully meets up with a woman) and climb up to the top to find a 009Antique Colombian Table Knife. Now drop down from the sign and continue to follow Sully.
Go up the stairs, through the crowd, and to the stand where Sully and Marlowe stop to talk. Go up to Sully and Nate will take his wallet. In the next cutscene, Sully catches Nate. While Nate has to give up the wallet, he's still able to get away with the key.