Across

 Across

####From one side to the other of something with clear limits, such as an area of land, a road, or a river:

e.g. She walked across the field/road.

e.g. They're building a new bridge across the river.

But when we talk about movement from one side to another but ‘in something’, such as long grass or a forest, we use through instead of across:

e.g. I love walking through the forest. (through stresses being in the forest as I walk)

e.g. I love walking across the forest. [Incorrect]

e.g. When my dog runs through long grass, it’s difficult to find him. (through stresses that the dog is in the grass)

####On the opposite side of:

e.g. The library is just across the road.

####In every part of a particular place or country:

e.g. Voting took place peacefully across most of the country.

Source:

Cambridge dictionary

Longman dictionary

Oxford dictionary