Design a square poster that encapsulates the essence of travel excitement by featuring an airplane, bus, and train in a harmonious composition. The artistic style should combine impressionism with digital art, allowing for soft brush strokes and vibrant colors that evoke a sense of movement and energy. Use natural light to create a bright and cheerful atmosphere, with the airplane soaring through a clear blue sky, the bus driving through a sunlit city, and the train gliding along a picturesque countryside. The background should include elements of travel, such as luggage, travel guides, and maps, adding depth to the scene. Focus on the intricate details of each vehicle, such as the reflections on the airplane's surface, the textures of the bus seats, and the sleek design of the train. Enhance the image with subtle post-production effects like HDR for depth and color grading for vibrancy. Add the text "Travel Excitement Awaits: Join the Adventure" in an elegant, modern font that complements the overall design.