On this page of the guide to The Witcher 3: Wild Hunt, you will find descriptions of how to complete the treasure hunt quests near the Crossroads Inn. These are minor optional quests related to, among others, finding the chest with a sword lying on the bottom, locating the cargo transported by the cart, and defeating the witch guarding the chest.
An Unfortunate Turn of Events
In this quest you must find cargo that fell from the boat. You will learn about the task by reaching the port in southern part of the map (M2,2). Start by dealing with nearby drowners. Then search for corpse at the water. Near the corpse you will find unsent letter. Read it from the inventory and dive in the nearby river. You must reach the chest lying on the bottom of the river. Watch out for drowners (Geralt can't defend himself while under water). In the chest you will find a Steel Sword Harvall.
In this task you must find precious cargo that was transported in a cart. You will learn about the quest by finding a corpse near a damaged cart in the southern part of the map (M2,3). Defeat the nearby foglet and investigate the corpse near the cart. You will obtain a letter. Examine the cart's surroundings and find another body. Near it you will find a small key. You can use it on the locked chest at the cart. Inside you will find a blueprint, runestone (it can be inserted into slots in selected weapons) and a glyph.
In this quest you must find a chest with valuable items. You learn about the task by reaching a corpse in the eastern part of the map (M2,10). Be careful as there are wolves and their stronger version called wargs nearby. Once the battle is over, search for the corpse and examine it. You will obtain Nilfgaardian's Notes. Read it from the inventory and go to the marked territory. The treasure you seek is guarded by a group of drowners. Defeating them shouldn't be hard. In the chest with main treasure you will find some florens and some Hardened Timber.
In this quest you must find a hidden treasure. You will learn about this task by reaching a corpse on the swamps in the north-western part of the map (M2,11). Deal with a group of drowners and, once the area is secure, search for the corpse. Near it you will find Bloodstained Key and a Bloodstained Document. Open the inventory and read the document. Activate witcher senses and start following the blood trail. It will lead you to a chest near a wooden construction. Destroy the obstacles with your sword or Aard sign. Open the chest (with the key you have previously obtained). You can take a blueprint, unique Headhunter steel sword and Tracker's Gauntlets.
In this quest you must find a hidden treasure. You can add it to your journal by reaching the swamps in the northern part of the map (M2,12). You must be careful as the place is guarded by a Bilge Hag on the 18th experience level. After slaying the monster, locate a corpse. Near it you will find a key attached to a crumpled note and a crumpled note. Open the inventory and read the note. Explore the territory marked by the game. The treasure you seek is well hidden, it's behind some barrels that can be destroyed with your sword or the Aard sign. In the chest, among other stuff, you will find a unique Luna steel sword.
In this quest you look for a treasure near the water. You can activate it by reaching swamps in northeastern part of Velen (M2,15). You should do it after you develop Geralt because a VERY STRONG basilisk is flying above this territory. After taking care of that monster search for the corpse near which you will find a slightly bent key and an unseen letter. Open the inventory and read the letter. Then, look around for the treasure chest (witcher senses will be helpful).