The main development of the town was in the Middle Ages, when it was under the influence of the Venetian Republic. Venice was the strongest state in the region from 1363 to 1797 and captured all coastal areas (the map).
Kefalonia was captured in 1500, and in 1593 construction of a huge fortress began. The length of the defense walls - 2 km! This can be best seen from the air.
The fortress was supposed to replace the castle of St. George, which could no longer cope with threats from Turkey and pirates. But due to a number of problems, in particular due to the lack of drinking water, it never became a full-fledged military object. After the capture of the Lefkada island by Venice (1684) and the founding of the city of Argostoli on Kefalonia (1757), the fortress completely lost its strategic importance.
Now Asos is a purely tourist center and the fortress is the main attraction. There are many hotels, restaurants and a small beach. There is a good paved footpath to the top of the hill, which offers scenic views of the authentic settlement and the coast.
You can go up along the shorter dirt path, use the maps.me app to find it.
The territory of the fortress is open 24h and access is free. Inside there are several historical buildings. These gates, by the way, are original.
At the beginning of the 20th century, the fortress became a prison, with the political prisoners after World War II. Although they just lived here, growing olives and grapes. These olive gardens can be seen now.
In 1953 there was a strong earthquake, after which people left the fortress.
On the territory of the fortress there are several good viewpoints, just go along this path and you will reach them.
Getting there: Asos is away from the main road. By car it is very easy to get to, parking lot is here N 38 22.613 E 20 32.274. You can get there by bus, but you have to look for information. There are no direct buses, you can go by bus ARGOSTOLI - FISKARDO and get off on the road above the village. Find schedule here https://www.ktelkefalonias.gr/en/. Departure from ARGOSTOLI (4 euros) - 11:30, arrival at ASSOS - 12:20. Then transfer to a local bus (2 euros). Theoretically, the local bus should go up and down. If not, you have to walk down 3.5 km, and then up. Also, you will need to know exactly when there is a return bus FISKARDO - ARGOSTOLI. A bit risky, but try.