The Ashdown forest is a beautiful area of England situated about 35 miles south of London and 25 miles north of Brighton on the South Coast. Although it's called a forest there aren't actually that many trees there. It's mostly a heathland made up of rolling hills of bracken and gorse with some wooded areas. Most of the trees were chopped down during the Industrial Reveloution (about 150 years ago?) to be used to fuel the Iron foundaries. The fact that the Forest isn't all densely wooded doesn't dimish from it's appeal at all. It makes a great place just to go walking whether you are into Pooh or not; in fact most of the visitors to the area (around 1 million a year) don't even realise that Winnie the Pooh is associated with this area. It's also not that large around 40 square miles and used to be a Royal hunting ground in byegone days (Henry VII and all that). It also has a wide variety of wildlife and plants some which are unique to the area.
As far as I'm aware all the places mentioned in the book are either real places on the forest or are based on real places. Most visitors on a Pooh hunt will probably be suprised by the complete lack of commercialisation of the 'Pooh effect' in the Ashdown forest. There are no signs showing you where certain places are and the places that do exist are generally only marked by small plaques that you could walk past without knowing - and many do. Personally this is something I totally approve of, and makes visiting the Pooh places a more enjoyable expericence and often a solitary one. There is information about Winnie the Pooh available and where to go, but you have to hunt for it, the best place is the Ashdown Forest visitors centre.
The Author of the books, A.A. Milne and Christopher Robin (real person who's still alive) lived in the small village of Hartfield on the northern edge of the forest. This is a very nice little village which has 2 good pubs :) and the Winnie the Pooh shop, which has just about every conceivable Pooh gift idea you can imagine. You can also eat at the Pooh tea shop where all the items of the menu have Pooh related names, with of course one of them being honey.
Not sure if this is actually 500 acres, but it is one of the most wooded parts of the forest and is located on the eastern side of the forest. A fair proportion of this land is, unlike the rest of the forest, private property so you'll only be able to walk in parts of it.
A very hidden little place that is simply marked by a large plaque on top of a large stone that comemorates A.A. Milne and E.H. Sheppard (the illustrator). From here you look out over a magnificent view of the countryside and is often refered to as the 'top of the forest'. This is located around the area of Gills Lap/Galeons Lap and is best reached by parking in the Enchanted Place car park and going for a small wander. All the car parks on the forest are simply small clearings in the undergrowth and are given names. There are a couple of other Pooh related named carparks.
Probably the most seeked and hardest to find. Pooh Sticks Bridge is located deep in a wooded part of the forest with almost no indication of where it is or how to get there, a bit of local knowledge can be invaluable. The original Pooh Stick Bridge fell down a while ago (20 yrs or so) and has been replaced by a newer style of of bridge which probably doesn't fit with most Poohites imagined picture of what it looks like, however it is still very nice all the same. The best way to get to it is from the village of Chuck Hatch and find the 'Pooh' carpark from there it's a reasonable walk through the trees to the bridge in the middle of nowhere. It's situated in a very nice little wooded area and with a gentle stream running beneath. Many a poohstick has been thrown from there.