What's more relaxing than riding a train? Throwing a glorified Frisbee at some stuff while legally drinking a giant can of craft beer in between rides on a train.
Seriously, you should keep reading even if you don't play disc golf, because I will convince you to play disc golf.
Why you should play disc golf:
It's cheap, it's the most relaxed sport ever invented, and it's a really good reason to go to the park. You can get a decent starter set of discs for under $30. Throw with your hips and follow through with the arm. There, you're an expert. Stop complaining and get on the train.
Why you should ride a train to play disc golf:
So you can enjoy a tall frosty one responsibly. Also, come on, this is a great idea.
TRY THIS COURSE: Drinks and discs at Dry Dock.

How to get there: Ride the A Line to 40th Avenue & Airport Boulevard. It's a 1.5 mile walk to Dry Dock's North Dock brewery and disc golf course. Remember, part of the appeal is the walking.
Course address: 2801 Tower Rd., Aurora 80011.
Can I get drunk? Yes. The brewery sells crowlers (giant cans) that you can bring on the course. Bonus: The train is your designated driver.
What's it cost: The course is free. The beer is not. Neither is light rail. But the course is free.
Hours: It's always open, but the tap room is open 2-8 p.m. on Wednesday and Thursday, noon to 8 p.m. on Friday and Saturday.
About the course: There are 9 baskets, but you can play alternate angles to make it 18. Budget a couple hours. I like this one! Some nice long shots, a few fun angles and varied terrain. And beer. Read more on DG Course Review.
OR TRY THIS ONE: Lakewood/Dry Gulch Park
This one is much closer to the light rail station, so it's good for a quick round. It's a really cool and surprisingly large park, tucked along a creek and the light rail line.
How to get there: Ride the W Line to Knox Station. Walk out onto Knox Court and head north for just a tiny bit. The first hole starts by the big sign just south of the parking lot, across Knox Court from the station. (Here's a course map and another)
Course address: 1260 Knox Court, Denver.
Can I get drunk? It's a public park, so you can bring 3.2 beer, but you can't publicly display it. Don't be a jerk.
What's it cost? Free, minus light rail.
Hours: 5 a.m. to 11 p.m.
About the course: A lot of long, fun shots on this one. The course makes good use of an interesting urban space, including a really fun throw from a hill and some scary shots across water. Be careful with your discs.
DON'T DO THIS ONE: Globeville Landing
I tried it so you don't have to.
How to get there: Ride the A Line to 38th and Blake. The park is a mile walk up 38th Street. You can also ride the South Platte trail by bike from downtown.
Course address: 38th Street and Arkins Court
Drunk/cost: It's a Denver park.
Hours: 5 a.m. to 11 p.m.
About the course: Not great. The baskets don't actually have baskets, the angles are weird and all kinds of people get in your way. Here's a map, have fun.
In conclusion:
These are an absolute ton of courses around here. DG Course Review is an excellent resource. Tweet at me if you want to play a round.