You can walk from the hotel to Qianmen and Tiananmen square. If you want take subway, you can get to Chongwenmen Station just next to the hotel to Qianmen Station (only one stop). Walk through the sqaure to the north, you can find Tiananmen in front of Forbidden City. You can find Beihai Park at the back of the Forbidden City.
To Summer palace: Take Subway Line 2 at Chongwenmen to Xizhimen, get off Xizhimen Station to catch Bus 634 or 375 to Yiheyuan Station, that is the Summer Palace.
To Temple of Heaven
Take Subway Line 5 at Chongwenmen and get off at Tiantan East Gate (two stops).
To Ming Tombs
Take Subway Line 2 to Deshengmen （Jishuitan subway station）, then change to Bus 919区 or 949 to Changping Guangxi, then change to Bus 314 to Dingling Dakou. You can see the Ming Tombs there.