One of the best cat-related investments I have made is their climbing tower. We put off buying one for years in fear they wouldn't bother even batting an eye at it, but boy were we wrong! They use every inch of it at some point each and every day. Of course, the very top post is the most sought-after place to nap. Many-a-times it has caused the cats to have a few little spats over who-sleeps-where.
I have a feeling we will be buying another one in the near future.