Design a stunning 3D rendering of a classic smartwatch, emphasizing its fitness tracking capabilities and customizable watch faces. The watch, adorned in metallic shades, should be placed on a polished office desk, surrounded by elements like a tablet and a stylish pen. The background should reflect a bright and vibrant office environment, with soft, diffused lighting that enhances the watch's features without overpowering the scene. Focus on the details of the smartwatch, showcasing its interface and design elements that highlight its functionality. This image should convey a blend of elegance and technology, appealing to professionals who appreciate both form and function in their gadgets.