In a country more famous for its coastline, about a million visitors each year venture inland to amble along these boardwalks and marvel at spectacular lakes and mountains. Plitvice Lakes National Park is the oldest and largest of Croatia"s national parks. The big attraction is the series of 16 descending, turquoise-colored lakes, connected by subterranean karst rivers, and above ground by streams and waterfalls. The lakes are separated by natural dams of travertine, which is created by the interplay of water, plant material, and bacteria. The water changes color from green to azure to gray depending on the angle of the light and the density of minerals and organisms in the water. About 11 miles of wooden boardwalk make it easy for people to wander among the lakes, falls, and caves that are open to visitors year-round.