which sentences are correct?
1, We climbed to the top of the tower, from which we had a beautiful view.

2, We climbed to the top of the tower, from where we had a beautiful view.

3, We climbed to the top of the tower, we had a beautiful view from.

see form a grammar book, the answer is 1 & 3, but I can't understand it, I think 2 is right.

Question

which sentences are correct?
1, We climbed to the top of the tower, from which we had a beautiful view.

2, We climbed to the top of the tower, from where we had a beautiful view.

3, We climbed to the top of the tower, we had a beautiful view from.

see form a grammar book, the answer is 1 & 3, but I can't understand it, I think 2 is right.

Answer

We climbed to the top of the tower, 1) from which (location) we saw a beautiful view. 
2. is OK, it is similar. and proper English. 
3. This one is not correct, because the 2 halves of the sentence do not flow well. The 2nd half does not follow the first one in grammatical sense.

There are many ways to say things in English, and many varieties of English on every continent of this world.

Answer

I agree with you.
You are referring to a location (top of the tower), so I would always use 'where', not 'which'.
In #3, I assume "from" should be "from there" ? If so, then it's correct , though I would never write it like that (I think the pause is too strong for a comma).