Comparative form: "more convenient" and "busier" are used to emphasize the differences in convenience and busyness between city attractions and rural attractions.
Present participle as reason adverbial: "in that we don’t need a car to get to them" uses the present participle as a reason adverbial to explain the popularity of city attractions, that is, the convenience of transportation.
Conditional clause: "unless we drive" uses a conditional clause to point out the limitations of visiting rural attractions, that is, it is difficult to reach them without driving, emphasizing the inconvenience of rural attractions.