If all dogs do indeed go to heaven, it must look nearly identical to Marymoor Off-Leash Dog Park. Dubbed "Doggy Disneyland" by locals, it features 40 acres of former farmland for Fido and his friends to go absolutely nuts. Border collies catch Frisbees mid-air. Beagles and Jack Russell terriers wrestle with one another. Labrador retrievers splash about in Sammamish Slough. The pups here party hard, scoping out as many playmates as possible. And, lucky for their owners, they nap even harder once they're back home. ERIKA HOBART 6046 W. Lake Sammamish Pkwy. N.E., Redmond