Bratislava, the capital of Slovakia, is set along the Danube River by the border with Austria and Hungary. It’s surrounded by vineyards and the Little Carpathian mountains, crisscrossed with forested hiking and cycling trails. The pedestrian-only, 18th-century old town is known for its lively bars and cafes. Perched atop a hill, the reconstructed Bratislava Castle overlooks old town and the Danube.