What are the best places to see on a visit to Jakarta? Where are the best beaches in Indonesia aside fr Bali?

I want to see exotic stuff in Indonesia. I have one day in Jakarta and if I'm lucky, I'd get to visit other places as well. I'm thinking of Bali but I want to know if thereare other interesting provinces/cities close to Jakarta that i can go to. I want to go snorkeling and maybe a bit of hiking. And i might hav to go alone so the sites have to be relatively safe :D thanks