The Grand Palace is a must to see attraction in Bangkok. If you have only 1 day in this city, then go there. Getting there is a little bit problematic, as the Skytrain and metro systems do not cover the area. The best option is to take a taxi or the boat. Be prepared that taxi or tuk-tuk costs twice more, so try to bargain your price before.
If you are looking for 1 day sleep around this area, check hotels on Khao San Road streat.
Some photos from The Grang Place and Wat Pho – the Temple of the Reclining Buddha in the area of the palace.