Nicoya is a large peninsula in the north west of Costa Rica that is famous for its surf beaches. It's one of the most touristy parts of the country.
Turrialba is an active composite volcano in Costa Rica, situated in the central province of the same name, and Irazu's neighbor. 
Poas Volcano during an eruption

Poas

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An active volcano that is 2,047 meters high and one of the most visited sites of Costa Rica.
The Rio Pacuare flows for roughly 100 kilometers from Talamanca to Siquirres, passing through tropical jungle along the way. The river is known for its rapids and, as a consequence, the rafting and kayaking that takes place on it.
Just beside Tamarindo, the most touristy spot here, Playa Grande is a bit more difficult to get to if you don't have your own means of transport but it isTHE surf spot in the area.
You can explore Costa Rica's most famous waterfall by following a trail through an enormous, purpose-built private garden. 
Siquirres is both a canton and a town located in the province of Limón (Atlantic coast), close to the very wild and natural park of Tortuguero.
Playa Ballena is the beach in the Marino Ballena National Park, a few kilometres from Dominical and Uvita, on the Pacific coast of Costa Rica.
Alajuela is a big city close to San José. In the shadow of the capital, it is an interesting departure point for visiting the North of the country and its volcanoes.
The small town of Sierpe is a little port lying very close to the mangroves and is a place you need to pass through to reach the Osa Peninsula.
A small, quiet town in the north east of Costa Rica, close to Lak Arenal. The countryside around Tilaran is quite flat, which I don't find very attractive.
The most popular of the Nicoya Peninsula beach resorts and a famous surfing spot..
The capital of Costa Rica, a town where it's always spring and the strategic joint between the two sides of the country.
The town of Parrita is a canton in Costa Rica's Puntarenas Province and serves as a transit point between Quepos and Jaco.
Puntarenas is a town of passage, for travelers and for locals, and especially for freight.
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Tour ideas for Costa Rica