The Gunung Gede mountain is 2958 meters high and doing a one (or more) day trek here is definitely worth it. On the way you will pass waterfalls, hot water areas, perhaps some monkeys, and at the end a very beautiful view over the crater, the jungle, and Cibodas (the place where you start).
The entrance fee for the Gunung Gede is 150.000 RP for tourists and 11.000 RP for locals. It takes about 7 hours up and 4 hours down, therefor many people overnight on the summit, two hours below the top.
The best, easiest, and cheapest way to reach Gunung Gede from Jakarta is by bus. When you plan to do a one day trip it is important to start very early, so leave around midnight from Jakarta. The bus to Cirebon (where you will start the trip) leaves from terminal Rambutan and costs 20.000 RP per person for a trip of around 4 hours. From this place you can take an angkot for around 10.000 RP per person to the base of the mountain (If you have lots of energy you can also walk this, it is around 5 km). In the base place you will find lots of warungs where you can drink a coffee or tea or have some breakfast before you get started. They won’t allow you to start before 5:00 AM.
After the ticket office, the area will very fast turn into a jungle. After about an hour you will reach the waterfalls (if you want you can also skip this because it is not on the main route to the top). Around 2 hours after this you will find the Air Panas (warm water), and another 2 hours later is the summit. In this place you can get some coffee and food if people are selling it there at the moment. From this place it is a steep 2 hours way up straight to the top. The way back goes twice as fast.
Good luck and don’t forget to bring a flashlight and enough water and food for on the way!
Going by train to Bogor is a very nice short trip from Jakarta. It takes about 1 hour and costs only 3.000 RP per person for a single way. In Bogor you will have much more green areas compared to Jakarta and the traffic is a lot more quiet. In the center of Bogor there is a huge botanic garden (the Kebun Raya Binatang). The entrance fee for these gardens is 25.000 RP per person. Inside you will find all kinds of trees from around the world (most of them from Asia). You can spend easily a few hours walking around here.
The Thousand Islands, also called ‘Pulau Seribu’ in bahasa Indonesia, is a group of 110 small islands located just outside Jakarta. From the harbour of Jakarta you can make a trip for around 2 days to one of the many islands close from here. The Tidung island is one of them and it takes around 5 hours to get here. There are many bungalows on the island where you can sleep and it has beautiful snorkelling places around. This is a very good place to calm down, since there is no traffic aloud on this island, only bikes. Also there is lots of good sea food available here and you will probably not find any foreign tourist here.
Another trip you can make is to Bandung. This is possible in one day if you go by car, but if you go by train it is better to stay a night over since it is quite a long trip. Inside Bandung, the main attractions are the warm water sources and the Tangkuban Prahu. This is an active volcano in the north of the city which can be reached by angkot, car, or bus. From the top you can see the crater and you can make a small hike down through some jungle where you will reach boiling water sources in which you can see sometimes locals boiling eggs. Walk slowly down because there is a lot of sulphur in the air on the way down.