The Venetian Lighthouse is located at the very northern tip of
Kefalonia, it's just outside the village of
Fiskardo and that's about an hours drive from the islands capital
Argostoli.
The easiest way to get to the lighthouse is to walk from Fiskardo, it'll take around 15 minutes at standard walking pace. Just remember to take refreshments with you as there's nowhere to get them once you leave the village although there is some shade along the coastal path.
The lighthouse itself dates back to the 16th century, it's a round building right on the coast, just behind it is a small villa and the whole site is overlooked by a more modern lighthouse that was built in 1892. The house and venetian lighthouse were renovated in mid 2018 with a new roof and new render on the walls.
There's not a huge amount to see at the Venetian lighthouse but it is sometimes possible to get inside and even up to the top level where you can enjoy the views of the Ionian sea.
Also on the trail from Fiskardo is the Christian basilica that dates back to the 6th century making it well worth the time, particularly if you are visiting Fiskardo anyway.