Answer
Uruguay has two land neighbors: Argentina in the west and Brazil in the north and northeast. Much of its border with Argentina follows the Uruguay River, so road crossings are concentrated around bridges. Along the border with Brazil, there are towns where the border runs directly through urban areas.
Buenos Aires lies across the Rio de la Plata from the Uruguayan coast and is connected to Montevideo and Colonia by ferry. Such a trip is an international border crossing, even if it takes several hours.
Before travelling by car, check your documents, insurance, the car owner's permission, and the rules for importing food products. Requirements depend on nationality and the type of vehicle, and a small crossing's opening hours may differ from those of a major crossing.