A place especially for skateboarding and inline skateboarding and sometimes even bikes. Most skateparks are unique in their design and they are usually the funnest places to skate. It's a good place to try a streetplant, learn to ollie, do a ho-ho, or perfect your kickflip to fakie.

markjugg runs Skatepark.org, was has all the info if you want to you get your own skatepark.

Skating at a park is one of the greatest things in the world, albeit it a little strange. It's a different atmosphere than street skating, and there's some unspoken rules and etiquette that need to be followed. Also, when a city gets a new skatepark, there's some fallout you should be aware of, but I'll get to that in a bit.

Rules & Regulations (plus some etiquette)

1. Pad rules: Every city park has their own rules: no cussing, no smoking, and the like. However, the really important one is the pad rule. Not many parks require full pads (knee, elbow, helmet), but most require at least a helmet. The question is how strictly this is enforced. Personally, I don't wear a helmet or pads, ever. I simply don't skate well with them on. However, I do bring a helmet with me wherever I go and if I'm asked to put it on I do, without bitching about it. Trust me, it's just easier that way. Some parks it doesn't matter. The park in my town says a helmet is required, but I haven't seen on yet. You'll just have to play it by ear.
2. Wait you turn: Simply that. Jumping in out of turn is called snaking, and it's rude as hell. If you watch a park for a bit, you'll notice the pattern people take dropping in or starting a run. Try to follow it, because if you start out of turn you're very likely to run into someone or have them run into you.
3. Get out of the way: There's nothing more frustrating to than to miss a trick or fall because some jerk is floundering around on something you want to hit. So, if you miss a trick or fall (and you're not hurt) get the hell out of the way. Don't pout, kick your board around, or start bitching. Just get out the way and gripe somewhere else. We're all sorry you missed your trick, but there's someone right behind you that wants a try.
4. Don't sit there: Please, don't sit on ramps, fun boxes, or ledges. You couldn't be more in the way. If you do decide to sit in the way, here's a word of warning: it's common practice to go full bore at someone sitting in the way. It's a not so subtle way of telling you that you probably need to move. There's benches everywhere, so please use them.
5. "Local" does not equal "asshole": You're not in a gang, and the park is not your turf. I've met some great people at skatepark, but i've met some assholes to. People will drive hours to skate a good park, so please don't ruin it by being a schmuck. It'll just give them a bad impression of your park.
6. Watch your mouth: Please, don't scream profanity whenever you don't land a trick. It's just rude and it'll piss off any parents who happen to be around. Feel free to unleash your hockey temper and toss your board around, but watch where you fling it.

Fallout
Be aware that when a city gets a skatepark a few things will change. First, expect the cops to be extra tough on you. Most cities just build a skatepark to get skaters to stop skating in the town, and will crack down hard on it. Second, you will be expected to care for the park. I've patched cracks and at other misc. things at my local park, and you should probably do the same. If the park starts to get skanky, the city will probably start cracking down on the rules (night skating, pads, etc.). Be forewarned: to most cities a skatepark is a bargaining chip, not a public facility.

I'm well aware that this just sounds like a lot of bitching, but it needs to be said. Over all things, have some damn fun. Skateparks are the perfect place to go apeshit and balls out, so don't let me stop you.