1. Shall we go where there is a shop?

2. We can get where there is water.
3. We have to walk where we can take a rest.
4. We drove where we can see many kinds of trees.
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Are the sentences all grammatical? Would you correct errors? Thank you.

1 - 3 are fine.

4 needs a past tense after "where" because of the past tense before "where"!