You can find the Dublin Treasure Hoard Map in the southeast corner of the Dublin area. Explore the coastline, go down to the water and explore the cliff wall (cave) to find an iron door with a padlock.
Use your Odin Sight and follow the path from the cave to the water. Using Odin Sight again to see the key under the water. Swim down, grab the key. Head back to the cave and grab the map.
Hoard Map Treasure Location
Head to Rathdown in the north of the Dublin region, and head east.
Use the Raven to check the pattern and layout of the fields that match the image in the clue. Treasure is buried in the corner of the eastern farm field.