This is a great trail, which travels alongside the Alaska Railroad right of way down Turnagain Arm, just south of Anchorage. It connects the communities of Bird and Girdwood, hence the name. ( I think it's called Bird because the original residents didn't know how to spell Ptarmigan, Alaska's state bird...) There are often sightings of Beluga whales and Dall sheep along the way, and always the entertainment of the ravens and magpies so common in Alaska skies. Some of the trail travels through wooded areas, and near the start of the path, at Bird Creek, there is a small state campground--a perfect place to park and ride. Or to camp overnight, if you are making this a part of a longer trip.
The trail is mostly flat, at least when it is following the railroad right of way. But about halfway along, the trail passes under the Seward Highway and follows the old road, now bike path, up and over a point of land. Even then, once you are up on the hill, out of noise of the traffic below, the path levels out until you get close to the Girdwood road turnoff. After that it is all slightly uphill to the town and ski resort, where there is a wonderful cafe and bakery to refresh yourself at!
And speaking of refreshing one's self, there are toilets at the campground, at a vehicular rest area just where the bike path goes under the highway, and at a rest station on the path very close to the Girdwood road intersection. This is a delightful afternoon interlude, only about 30 miles south of Anchorage. One more proof that the nice thing about Anchorage is that it's only a short distance from Alaska!