A ten minute boat ride across choppy waves is the Beruwala Lighthouse, also known as the Barberyn Lighthouse because it's situated on Barberyn Island. It's pretty old, with its construction being completed in 1889. Interesting to note that it survived the Boxing Day Tsunami though, and is still fully functional.
Get onto Maradana Road from Galle Road and ask anyone from the area for directions on how to get there. You'll have to barter a price with the fishermen to ferry you to the island though. Prices start at Rs. 2500 for a roundtrip, but can range to around 3000 or more (depending on how foreign you seem, probably).
Thanks to some visitors who'd made some sort of fuss a few months ago, the lighthouse is off-limits to visitors now.
The lighthouse keeper is quite firm about not allowing even a foot inside the tower, and the door granting access is firmly locked and bolted. He did give us free reign of wandering around the island and its insanely rocky shores though.
The island itself is very quaint and looks heavenly from the mainland (heh). It's quite reminiscent of Kirrin Island if any of you've read the Famous Five series, except instead of a ruined old castle we get a lighthouse with a caretaker. I know this isn't really the same thing, but there's a definite feeling of nostalgia.
There's a ruined old structure (an old house?) close to the pier, and a sandy, crushed-sea-shells dusted path leading through bush and palm trees to the lighthouse.
It's quintessentially tropical.
You can take a dip and splash around, it's quite, quite secluded (at least when we went, we were the only visitors on the island. And there was one caretaker there).
I've heard a few people say they've camped there as well, but we wouldn't recommend it unless you check beforehand and get the necessary permits!