Although not as populous as the capital Samarinda, Balikpapan is Kalimantan's only truly cosmopolitan metropolis thanks to a long history of oil money and foreign workers, and that makes it worth a look in its own right. It's still seen largely as a stepping stone to Samarinda, Derawan or Banjarmasin, but a night in Balikpapan's club scene will give you a whole new perspective on Borneo.
While the port area is a bit grimy, for the most part the city is clean and vibrant, with several enormous shopping plazas and some decent beaches. Midrange to high-end hotels with reasonable rates abound, and a social scene exists in the form of restaurants, hotel bars, live-music venues and the odd nightclub.
Overall the city makes a fine weekend break and a great place to begin or end more adventurous travels.