biking in central park

Ok, so my husband and I get up at the butt crack of dawn on a cold soon to be drizzly sunday morn. Hes got a NYRR 4 mile race in the city, and I figure I'll tag along and bring my bike. I'm trying to do long rides on sunday morning for my upcoming tri in mid June. So we travel to the big apple, even bringing our dog, and he dog sits and registers for the race while I start out on the 6 mile loop around central park. I planned on doing it three times. Well, I barely managed to keep my mph at under 4, and my legs still feel like jelly! I've lived here for 14 years and have been in that park numerous times. So, let me share my surprise with those of you who haven't......central park is NOT flat. Just because its in the middle of the busiest cities in the world, it's not like walking along window shopping! But, I did it, and I'll do it again. Just was a bit surprised, thats all!