Dolmabahçe Palace is between Beşiktaş and Kabataş, where you can get easily.

If you are staying at a hotel in Sultanahmet, get on a tram and get off in the last station; Kabataş. Then walk through Bosphorus for 5 minutes, and you will see Dolmabahce Mosque, Clock tower and behind them Dolmabahçe Palace.

If you are staying at a hotel in Taksim (Beyoglu), you can walk for 15 minutes down hill to Kabataş. Or you can get on Finuculair and go Kabataş and walk through Dolmabahçe Palace.

Enjoy visiting one of the greatest Ottoman Palace in Istanbul. Also used as main palace after Topkapi Palace.