Know that age restrictions for car rentals can vary by city as well as by company. Don't assume that because you rented a car through a certain car rental company recently in another city means that you'll be able to rent through that company in any city.
Call car rental companies in the city you wish to visit. Ask specifically about restrictions for older drivers. Be sure to write down the name of the person you spoke with, and the time and date of your call.
Tell your real your age when you make the reservation. Your driver's license will be checked when you arrive at the rental counter, and you don't want them to then refuse to rent to you based on your true age, leaving you without a rental car. Better to know in advance and find a car rental company that will rent to you.
Consider other forms of transportation if you've exhausted all your other options. Hiring a driver to take you to see certain sites you want to visit for a day might be less expensive than renting a car for a week. In larger cities, public transportation might also be an option.