The original station was a rather ornate brick building with a small tower and it was located right where the district court is located today. I have never seen the depot as it was gone long before I was born, but there are plenty of pictures of it. The station at Anderson Regional Transportation Center has some architectual features that, I guess, are supposed to remind you of the original one.
Portions of the Woburn Loop ROW still exist. In fact a large portion of it follows the Middlesex Canal. A good reference point to start is if you go to Central Square in Woburn and go down Wyman Street. As soon as you pass the Square you will see the ROW and the Canal. On the right is a fairly newer looking private home (probably built within the past 30 or 35 years). This was the location of the Central Square Depot. If you look to your left from Wyman St., you can walk the ROW back towards Woburn Center. The Canal will be on your right.
You can barely make out the ROW also from Winn St. If you are heading from Woburn Square down Winn St. towards Burlington, and not far after you pass Lannan Chevrolet, you will see it. It crossed Winn St. at a pretty sharp angle and is more prevelant on your right. As I recall there is also a Gibbs Gas Station (might be under another name now) next to the ROW. As I also recall, that portion of the ROW had a lot of brush on it, but if you know the signs of a ROW, then you will see it.
On the end of the Woburn Loop that lasted until 1981, a good portion of that ROW has been obliterated. There once was a bridge by Andea's Pizza, but it was taken out and was replaced by fill. At the Stop & Shop in Winchester there was another steel bridge (it was next to the main line bridge that is still there) that was taken out along with the fill. In fact there was an addition to the Stop & Shop that is now on the Woburn Loop ROW. This was the point where it connected with the Main Line.
As a kid (around 5 years old), my Mom, brother, and myself would take the Budd cars from that cinder block "depot" from the end of the line and go into Boston every so often. This was around 1973 and I remember how ratty those Budd cars were at that time. I remember very clearly all the grade crossings in Woburn and going by that round apartment building that is in Winchester.
Anyways, hope this all helps