Resident Evil 4/Chapter 4-3

Ruins
You are now outside at the end of a long walkway, and it’s nighttime. The Merchant has set up a stall here; get two barrels on his left, do some tune-ups, and save at the typewriter if you want. Take the “Letter from Ada” from the doorway. It's from Ada and she warns you that you shouldn't let the parasite eggs hatch inside you (that ship has sailed), and if they have you'll need an operation to remove the parasites before they mature.

Make your way down the path to some ruins; you get a quick look at the tower ahead. Shoot the nest in a tree about halfway for a Spinel. A few villagers are wandering around but on their own and easy to defeat. Further on there is a large group of them gathered around a fire. Look for a ladder on the left and climb it to a platform where you can observe them undetected, then toss a Hand Grenade to get most of them at once. There is another platform on the right where you can do the same thing but are more likely to be spotted. If you don't have a grenade then just attack from a platform and take them out when they try to climb the ladder. Search for items. The door to the next building is in the left corner, but it's locked and you need an item to unlock it.
 * Spinel on a table to the right as you go through a doorway
 * 2200 PTAS on a table to the left just after this
 * Barrel in a left corner past this
 * Velvet Blue and 1800 PTAS in the remains of a building on the right
 * Barrel on the right platform
 * Barrel in the right corner at the far end
 * Box inside the wooden shack at the far end

Go into the wooden shack and turn the crank to open a hole in the ground, then climb down.