Depends on the type of bike that you have. The Fort to Fort trail is a really wonderful ride if you can go on off-road type situations (still very flat and not difficult on most bikes). Another easy option is to do a loop between Allard Crescent / 208 St / and 96 Ave. Take a look at Google Maps and you should be able to see that it's just a giant loop with Derby Reach park as a wonderful stop/finish point.