First I want you to know that Aso is not just a volcano, it is a large and diverse area. Here there are fields and farms, hot springs, waterfalls and many wonderful paths going up and down the hills providing a beautiful view all year round. Inside the hollow there are also several volcanoes with the landscape being mainly volcanic desert.
The main sightseeing spot is definitely the still active volcano Naka-dake. I think the experience will be different every time you come here because the volcano changes constantly, when I came here the scene was quite impressive. If you want to see and feel the power of nature, you must go here, witnessing the volcano with its own eyes so that it is smoking, almost scary. Please bring a lens to observe the volcano's surface more easily, you can watch a short video below because there are many things I cannot describe in words.
Visitors can reach the top of the active volcano by car or bus. The main road ends at a parking lot next to an old, unpromising suspension station. I didn't find the hanging settings but you don't need to access them either as you can walk them by yourself. Reduced travel time by 10 minutes, the road going up is better maintained and not too steep. If you don't want to, you can continue using the car but will incur a ¥600 account fee for the remaining extended distance.
Most people just come here, look over the volcano and then go home. Sadly, there is much more here for visitors to explore. Another unique hands-on experience you shouldn't miss is the volcanic desert right on the edge of Naka-dake. There is another detailed article about it that you can find.
The Japan Geoparks Organization also introduced a number of exploration progresses covering a variety of topics. This is a guide to auto tours, you can download them from their website (Geography Tourism Course). Visitors can also go to Aso station, which always updates the latest information on volcano status, train and bus schedules, etc. in English. Other exploration itineraries may include the impressive Kusasenri-ga-hama (草千里ケ浜) plateau. It is a large grassland with a few ponds and grazing cows and horses. A short additional walk will take you to Kijima-dake (杵島岳, 1270m) which offers stunning views of the entire Aso hollow, you will also see Komezuka (米塚), a prominent volcanic peak work. Eboshi-dake (烏帽子岳, 1337m) is another peak where you can admire the surrounding scenery from a different perspective.
The most convenient means of transportation is by car because visitors can freely explore the surroundings. Shuttle buses only operate at the main attractions as well and infrequently.
When did you come here? The weather in early April is still quite cold, however there is enough hot water here to keep the system warm for me! However, the scenery in some areas will probably be more impressive as soon as spring turns green, especially the area around the Kusasenri-ga-hama plateau.
Where? I highly recommend Shukubo Aso, a friendly family farm near Aso Station. There is also a small, low-cost hotel suitable for backpackers called Aso Base Backpackers.
How long should I spend here? You should spend at least 2 days here, maybe 3 if you plan to climb a mountain or two. If you only have time for one day (like me), no problem, the trip is still well worth it, but if possible I would still like to stay longer.
Due to constantly changing volcanic activity, access to the volcano may be prohibited. Don't worry though, because like I said, there are plenty of activities you can do here and one of them is definitely observing the mountain from afar. Take advantage and if you have any questions let me know in the comments.