Isengard:

Another fortress in Rohan, built by the Númenoreans, Isengard was extremely defendable, and the key to the defense of Rohan, as was discovered in the time of Helm Hammerhand, much to their dismay. It was always part of Gondor, even when Eorl was given the land surrounding it. Isengard was given to Saruman in the year 2759 of the Third Age, by the Steward Beren. Isengard was at least partially destroyed by the Ents in the year 3018 of the Third Age. In the language of Rohan, Isengard was Angrenost.

Ithilien:

Ithilien was once a beautiful area of Gondor, often called the Garden of Gondor, though it was eventually abandoned after the taking of Minas Ithil. Ithilien was located between Minas Ithil and the Anduin. Even in the years of the War of the Ring, the hobbits could see the remaining beauty of Ithilien, though it was no longer tended and had fallen into ruin. After the War of the Ring, Ithilien was given to Faramir, by the King Elessar.

The Hobbit
The Lord of the Rings
The Silmarillion
The Complete Guide to Middle-Earth by Robert Foster
The Unfinished Tales