Составьте придаточные предложения, соединяя два простых, употребите нужный по смыслу союз. Last year I went to Paris.

 Last year I went to Paris where I stayed for a week.

It was a lovely experience which I will never forget.

I stayed with Louise who is my French cousin.

She introduced me to Pierre whose knowledge of Paris is amazing.

I loved the boulevards which are so wide and elegant.

The Eiffel Tower is, of course, a great sight that is famous all over the world.

My favorite building, however, was the Invalides which was built in the 17th century.

At the end of the week I thanked Pierre who had been very kind.