The Kvarken Archipelago (Merenkurkun saaristo) is an archipelago in the narrowest part of the Gulf of Bothnia, between Finland and Sweden. Along with the neighboring High Coast of Sweden, it has been named a UNESCO World Heritage Site. The site is located in the municipality of Korsholm, off the coast of Vaasa.
Once weighed down by immensely heavy glaciers that melted after the end of the Ice Age, the Kvarken area is undergoing extremely fast uplift (by geological standards), with land rising about 8 mm per year — enough to create 1 square kilometer of new land every year.
Unlike the rest of Finland, the area is exclusively Swedish-speaking, most exceptions being summer cottagers.
The archipelago consists of some 6,550 islands. The largest of them, Replot (Raippaluoto), is Finland's 8th largest and houses the vast majority of the islands' population of some 2,500 people, but it's (just) outside the official World Heritage Site area. Björkö, containing the small idyllic seaside village of Björköby, is in the midst of the site.
Flora and fauna
As could be expected at a seaside location, the area is windy, and it's a good idea to pack a warm coat or jacket even in summer. However, the area is one of the sunniest in Finland.
The best place to start your visit is the Terranova - Kvarken Visitor Centre, located not in the archipelago, but in the nearby town of Vaasa. Road 724 (Yhdystie-Alskatintie) connects Replot with Vaasa, starting from a roundabout connected to highway 8 east of the city center. The road goes to the Replot bridge, and most other road connections (Björkö or Panike) are through Replot. The exceptions are the northeastern islands Köklot and Värlax, to which the road begins just shy of the bridge on road 724. A few of the islands near the coast are accessible by car, but for most of the smaller and outlying islands, you'll need to get a boat.
Adults (over 18) need a fishing permit (kalastuslupa), which can be purchased at R-Kiosks. If you have a Finnish bank account, you can also buy them online.
There are four designated nature trails for hiking among the islands of the archipelago. Canoes and kayaks can be rented at some of the nature stations, and are an excellent way of getting around.
The best way to see the heritage site is by boat. Because the seas are shallow and rocky, and because new rocks and skerries appear often, it is recommended to have a local to navigate. Boat tours are available, see a compiled list here: 
There are seasonal boat cruises to the heritage site (maailmanperintöristeily: ), arranged from late June to mid-August. Booking in advance is required. Regular cruises to Valsöarna take 5 hours, costs 55 € for adults, and departs from the Björköby harbor (Svedjehamn). Regular cruises to Västerö/Mickelsöarna take 7 hours, cost 58 € and depart from Abborgrund quay, Västerö. There are also individual cruises. A short cruise (2 h) on the M/S Corina departs from Berny Cruising Services's quay next to the Replot bridge, and costs 16 €.
The archipelago of Valsöarna (Finnish: Valassaaret) is a good birdwatching site, being a stopover point for a rich variety of migrating birds. However, Valsöarna are one of the most remote of the islands, and is accessible only by boat. Valsöarna are visited during the boat cruise mentioned above, otherwise you need to hire a boat.
There is a Sale grocery store and a Shell gas station shop in Replot church village near the bridge and a small shop in Norra Vallgrund in the southwest. There are cafes in Björköby and Replot.
There are five "Nature Stations" throughout the archipelago that offer basic accommodations. They're intended primarily for groups, and reservations are essential.
Camping is allowed throughout the archipelago, but open fires are only allowed at designated spots.
As in any sparsely populated place, roads are often narrow, unpaved and locals drive fast. The land uplift has one unique effect on boating: new rocks and skerries appear occasionally. This and the shallow seas mean that it's best to have a local guide when boating. Also, the distances often surprise new visitors: you usually need to drive tens of kilometers to most places.