You can see most of BSB's sights in a day. One of the most impressive things in the whole country is the Omar Saifuddin Mosque. At night it's particularly stunning with green lights illuminating the dome, casting a pleasant reflection in the pool below. Something not to miss if you like all that is gold and glittering is the free Royal Regalia Building, a museum of the sultan's treasures. You can see the sultan's coronation regalia as well as a myriad of gifts presented to His Majesty by various heads of state.
If you need to pick up some groceries or just long for a stroll in the mall, you can shop at The Mall, Brunei's only shopping mall. It's right across from the mosque and although very sterile, it has many brand name shops.
Currency in Brunei: Bruneian Dollar (BND)