Designing a turtle habitat is quite difficult as it needs both a land and a water area. Their habitat should provide enough space for a pool deep enough to comfortably swim in and a dry basking area where they can rest clear of the water and sun themselves. Here is a link from where you can find more information:
http://petturtle.htmlplanet.com/habitat_setup.html

 A pet turtle’s habitat is the house you develop for it in your home. It can be indoor as well as outdoor. Indoor habitat is an aquarium or tank. Tanks size should be big enough to keep a turtle comfortable while moving here and there. Normally glass aquariums are used. They look beautiful and we can easily enjoy the movements of a turtle inside it. And an outdoor habitat is a garden pond. It is better to make a rock in its tank or pool, which is above the water level. Turtle can climb and make itself dry for a while when it does not want to swim in the water.