Puntarenas is a city and area in Costa Rica, located on the Pacific Coast, or more precisely, on the Gulf of Nicoya.
But first, a jurisdictional matter to clear up. In Costa Rica, "Puntarenas" refers to a province, the head canton of that province, and a district within that canton. And a physical feature, as well! It perhaps would be more correct to title this "Puntarenas, Puntarenas, Puntarenas, Costa Rica", but that would be quite a mouthful!
Puntarenas, which translates to "Sandpoint", is, as its name suggests, a long narrow peninsula. It is surrounded by the Gulf of Nicoya on its southern edge and a small estuary on its northern edge. The peninsula is about 5 miles long and is a bit over 2000 feet wide at most. Given that the peninsula is located in the tropics, and is surrounded by water, the temperature is uniformly hot, but not scorching. Much of the peninsula is also fronted by excellent beaches, as well as a boardwalk with many restaurants, and other accessories of tourism.
One thing about that tourism: Puntarenas is located about 50 miles west of San Jose, Costa Rica and the Central Valley, or about 2 hours on a slow driving day, and as such, is the easiest place to reach for locals on the coast. It is a busy tourist town for day trips and longer vacations---but for the most part, it seems to be the vacation spot for Ticos, and most foreign tourists seem to visit towns that are further away, such as Tamarindo, Jaco or Quepos. Puntarenas, both the peninsula itself, and the adjoining areas, seem to be a little bit more down to earth.
If you are ever spending an extended amount of time in Costa Rica, and want to make a quick and cheap day trip to see what a tropical sea looks like, or just want to enjoy some sand and some warmth, Puntarenas will be an obvious destination.