Olympic Sports Park is really pleasant. If you are stopping in downtown Miyun, such as on your way back from Simatai or for whatever reason, if the weather is nice it is well worth whiling a few hours here, walking by the river. Signs in Chinese say don't walk on the grass wearing shoes. I took this to mean you can walk on the grass if you take off your shoes. The grass is soft. The whole place is a wide green space, clean and very pleasant.
90 minutes NE of Beijing is the Nanshan ski resort - ten minutes from the city of Miyun. Open from around November until Chinese New Year (possibly longer), it relies upon a barrage of artifical snow-making machines and blowers, but it provides the urban rich in Beijing with the opportunity to ski on 'real' snow. The ski runs aren't extensive, but there are sufficient runs to keep all but the most hardened skiers happy, and there is even a fierce Black route off the highest hill.
If skiing is not quite yo9ur thing (it isn't mine, but I have two kids who love skiing), there are other activities,including a 1300 metre toboggan run, snowmobile rides and other gentler activities.
If you are used to European or American ski resort prices, you might want to consider learning to ski here on the outskirts of Beijing, where you can get instruction for just RMB100 per hour. I was taught to ski sufficiently to get down the easier slopes in just 90 minutes.
The majority of the visitors are day visitors, andmany are on corporate outings, so there are a large number of suicidal skiiers who turn up, strap on skis and head for the top of the mountain. However, there are a lot of medics on and around the slopes to pick up the pieces, and if you have a heavy fall, you will have assistance in 30 seconds. However, beyond the well-meaning ski-slope medics, the First Aid facilities seem terribly limited, and the nurse who attended to my daughter wanted her to go straight off to hospital for X-rays...it was clearly just a bruised leg. There is a big difference between being cautious and simply abdicating responsbility towards the nearest hospital. The ability to make minor medical decisions may be quite important for you!
Route S205 north of Miyun takes you into the deep contorted valleys and twisted gorges of the river that feeds into the Miyun reservoir (the huge dam that you see after taking off from Beijing Airport).
These valleys are peaceful and beautiful - small villages, dusty tracks, crab-apple orchards and fields of maize and peanuts.
Water runs through the valley all year round (unlike some of the rivers to the north-west of Beijing).
You can walk pretty much where you want, with high mountains towering above you, down the valleys and up shepherds paths.
One paricularly beautiful valley can be reached by taking the first turning after the second (longer) tunnel heading north (around 30 km north of Miyun on S205) and following the road down to the river.
There are waterfalls al along this valley, signposted from the road, plenty of restaurants and cafes, and a lot of fruit to buy!
If you have the book "Hiking around Beijing", this area is the first stretch of the 'Scenice Drive' (Walk 13).
We tried to go to Tianmen Shan in western Miyun County. Local villagers blocked the road to the ticket gate with stones and with farm implements as weapons. It turns out the villagers blocked the road to coerce more money out of the tourism development company (as though living at one part of its base means they own the mountain). Usually, I stick up for the underdog, but in this case, the villagers had no legal or moral right to block a road that the villagers themselves did not build, but that they make use of and profit from. We called the tourism association and they did nothing to help us. We had to turn back. Over and over, our group found people in this area were less pleasant compared to local people in other places around Beijing. Most of the time, I enjoy travel and meeting new people. I advise tourists that there are plenty of better places to go for overnight trips around Beijing besides Heilongtan, Tianmen Shan, and the vicinity.
This place charges too much for entrance to the park. It is a nice park with a stream but nothing that special. At the back end of the park at Heilongzhentan there is a long-running scam which has not been shut down. It is a raft ride, pay in advance, which the operators claim will take you 60 meters into a cave. There is no cave and the ride itself is ridiculously short, basically around a corner. We found out later that this is a well-known scam to the locals, but nothing is done to warn people or to shut it down.
Generally, We found locals in this area of the Miyun countryside less helpful and more money-grubbing than anywhere we have traveled before. Also, somewhere along the way they learned to try to ask for a tip on top of the already high prices for services.
Unique Suggestions: If you go to Miyun, enjoy the clean and pleasant downtown, maybe go to the reservoir, but don't wander further afield without a knowledgeable guide, even if you speak Chinese as we do. People will try to rip you off.
Fun Alternatives: The alternatives include the pleasant Miyun Olympic Sports Park, and perhaps sections of the Great Wall in eastern Miyun. The villagers in western Miyun, including our at our country inn, were just so greedy that it put a damper on our overnight trip.