On this page of our guide to The Elder Scrolls V: Skyrim we have prepared a detailed description of the second and third treasure map. You will learn how to read maps and where they lead. These are not fully-fledged side quests, but optional activities that allow you to reach hidden chests with valuable loot.
Treasure map II
South-east of Winterhold, between snowy wilderness, you should find the Journeyman's Nook. Head inside, defeat the bandit living there and afterwards take a look inside the bag beside the campfire (screen below). The treasure map is inside.
The drawing will point to two towers rising above the water - the treasure should be on the ground, beside one of them. There's only one such location in the whole of Skyrim - Valtheim Towers found east of Whiterun (screen below).
Approach the area guarded by bandits and take a look at the towers from the waterfall's side. At the bottom of the left tower there's a chest with lots of random, powerful items.
Killing the bandits isn't obligatory - if you want, you can just take the valuables and retreat from the dangerous location.
Treasure map III
South-west of Windhelm you will find the Riverside Shack. Approach it and you will be attacked by a sabretooth tiger who has eaten the shack's owner. Kill the beast and find the next map in the corner of the room.
The drawing on the map points to Solitude Lighthouse. Head there and find the chest between rocks. It's beside the seashore, north-east of the lighthouse.