In a dutch oven over medium heat, cook bacon until crisp; remove, reserving drippings. Drain bacon on paper towels and set aside.
Add celery and onion to the bacon drippings. Cook over medium-high heat for 3 to 4 minutes or until tender, stirring frequently. Drain.
Add potatoes, broth, water, caraway seed and cooked bacon (broken into 1-inch pieces). Bring to a boil. Reduce heat and cover. Simmer 10 minutes or until potatoes are tender, stirring occasionally.
Meanwhile, place bread slices on an ungreased cookie sheet. Broil 3 to 5 inches from heat for 2 to 4 minutes or until toasted, turning once. Sprinkle each bread slice with about 1/4 cup of swiss cheese. Broil 1 to 3 minutes more or until cheese is bubbly.
To serve, ladle soup into individual bowls. Top each bowl with 1 cheese-topped bread slice.