Home to the famous Matterhorn, Zermatt is known for world-class hiking, skiing, mountaineering, and more. Zermatt is car-free (except for the small electric taxi cars and buses), so you have to park just north of the valley in Täsch and take the train shuttle to Zermatt from there. There is no public road to Zermatt. There are numerous parking garages in Täsch, including one right at the train station.
The Matterhorn Glacier Trail is a relatively short hike, but it packs a number of amazing views. It begins at the cable car station Trockener Steg and ends at the Schwarzsee station. You'll either need to take the cable car or hike up and down from these points. The cable cars are relatively pricey, but the views from the hike are incredible and well worth the price. The hike can also be done in the reverse direction, just remember that Trockener Steg is at a higher elevation than Schwarzsee, so the hike will be net uphill if you hike in reverse. This hike is a good choice for families with children, as it's not particularly taxing but it offers great views of mountains, lakes, rivers, and glaciers. The trail also has over two dozen informational signs along its length that provide information about the glaciers and geography of the area.
To get to the start of the hike, you'll need to take the cable car from Zermatt up to Trockener Steg. There are two main cable car routes for this; the direct one goes from Zermatt - Furi - Trockener Steg. However, it is likely you will take a slightly longer cable car (with better views!) that travels Zermatt - Furi - Schwarzsee - Furgg - Trockener Steg. It's a bit confusing, but basically you can just sit on the cable car until the end and enjoy the views.
At Trockener Steg there is a restaurant, shop, and some maps. The bathrooms here are flush toilets, but they do not guarantee that the tap water is potable, so you should fill your bottles beforehand.
When you exit the building, you should see the Wanderwegweiser, the bright yellow hiking trail sign. Follow the sign toward Schwarzsee. The trail, marked by white-red-white blazes (which mark all trails classified as "mountain hiking"), will lead down toward and around the lake Theodulgletschersee. This alpine lake is filled by a large waterfall coming straight from the glacier barely a quarter mile away. The cascades are altogether over 30 meters high, and they are very impressive in summer as the glacier melts.
On the western side of the lake, after about 0.7 miles of hiking, you will pass another yellow hiking sign. The trail continues straight here; however, if you are adventurous, you can take a short excursion to the Theodulgletscher (Gletscher = glacier). There is a short alpine hiking trail, poorly marked with white-blue-white blazes, leading to the glacier. The glacier is in sight, so you can simply scramble around the rocks and create your own path to reach the glacier. This is where the river leaves the Theodulgletscher, and this creates a huge ice cave in spring/summer. You can't (and shouldn't) really walk into the cave because of the river, but it's impressive to see. In summer 2018 the cave was at least 20 feet high. (It goes without saying but of course be careful near the glacier! The caves can collapse at any time. Use caution!)
After the Theodulgletscher, the Matterhorn Glacier Trail leads down past several smaller lakes over rolling, rocky terrain towards the Furggsee. After about 1.5 miles the trail begins heading more steeply downhill and towards the Furgggletscher. The trail passes within about 100 meters of the glacier, and it is again worth taking a short detour to get a closer look. Be cautious, as the glacier shifts and rocks slide off every few minutes.
From here the Matterhorn is extremely close. The east face towers massively above the trail. The Hörnlihütte, where many hikers and mountaineers stay overnight before summiting the Matterhorn, is also visible from here.
The trail crosses a bridge over a relatively swift glacial river. After the bridge, the trail heads uphill towards Hirli, where another hiking sign awaits. There is a small cable car station here, but it does not run in the summer. From here it is only about a half an hour walk to Schwarzsee, and it is all downhill. The trail switchbacks back and forth, crossing a gravel ski piste once. The Matterhorn is behind you now - don't forget to turn around and enjoy the view!
On a clear day the Schwarzsee station will be visible from quite a distance. As you approach, the lake Schwarzsee ("black lake") will come into view, hidden behind a small rocky ridge. There is a small chapel at the lake, and sheep can sometimes be found grazing nearby.
The total time estimate for the hike is two hours from Trockener Steg to Schwarzsee, or two hours and 15 minutes in reverse. However, you can spend as much time as you want exploring the area - it would not be unreasonable to spend six hours there (assuming you start early enough). But if you are pressed for time, two hours is a reasonable estimate for the average hiker.
The Matterhorn Glacier Trail ends at the Schwarzsee station, but there are options to continue your hike:
For information about these trails, check out the official Swiss online map. For information about the Matterhorn Glacier Trail, as well as current weather and cable car timetables, check out the Zermatt website.
Be sure to do a bit of research before you hike here. The cable cars are useful, both for convenience and as a backup plan, but be aware that the last descent is often as early as 4:30 p.m. With a bit of planning (and maybe some good weather), there's no doubt you'll enjoy your time in Zermatt!