Hiya!

So this is my "On a Rail" Achievement map. At first I used it for myself, but I decided to upload it.

Anyways...
The run time is about 2:13 seconds.
I tried to tamper with the environment as little as popular.
About half way I marked a large, nearly-flat clearing I found (but there is a lot of annoying tall grass).
Towards the end, I built an aqueduct-ish thing to cross a wide river. From the aqueduct, you can see an untampered-with, natural NPC village with a lot of wheat.
This map is also great for working on archery and fighting skills. I leveled up countless times while playing.
The pattern of the track is 2 boost, 2 normal, 2 boost, 2 normal, etc. This way, it runs on a constant speed where it isn't so slow it's boring, but you can still appreciate the scenery.

At the end, I put other achievements you can get, like fishing, cake-making, and pig-riding.
Also at the end, there is a small display of fireworks. I've somewhat followed a design from a video. To reload it, delete one block of redstone dust where the lines intersect, wait a second for the power to turn off (if it does not turn off try with a different piece), and then replace the piece. Then, place 8 TNT directly above the water, and one on the block in the center.
For more guidance, consult the end of the video.