Walking will always be a good form of exercise but if for some reason you can’t bring yourself to walk today, try hopping on a bicycle instead.
Biking is not only a fantastic form of cardio exercise it also works out most major muscle groups.
Depending on the type of bike riding you decide to try, a little research may be needed.  Not sure what size bike you need? Your local bicycle shop is usually a great place to start, read Cycling for Beginners: How to Choose the Right Bike and Equipment or check out Bike Buying Guide. 

Limited on storage space, a folding bicycle is designed to fold into a compact form making it easier to transport, store and travel with. 
Airline baggage regulations often permit folding bikes as ordinary luggage making traveling to other cities or countries a bicycling adventure. 
There are many good quality makes and models to choose from that come in a variety of sizes, performances and prices. 
Again a little research will be needed, start with the  Bike Buying Guide and check out 10 Reasons Why a Foldable Bike is the Best Commuter Bike. 

If you want to try bike riding but are not quite the adventurous type, try an in home exercise bicycle.
The  Exerpeutic Upright Exercise Bike comes with:
Adjustable Seating Comfort - to fit anywhere from 5'3 inch to 6'1
Heart Rate - Heart Pulse Monitor
Compact Design - Folds for easy storage and can easily be moved with the included transportation wheels.
The wheels make it possible to move it outside, onto the porch or balcony so you can enjoy the sun and possibly have your own creative adventure.