These towers were used to keep time in ancient times. The Drum tower houses a few devices for measuring the passage of time including this thing...
The containers are filled with water, and each contains a hole of a specific size where the water flows out. They measure the passage of time by the amount of water that flows out of the hole. When a specified quantity of water flowed out of the device, they knew a certain amount of time has passed.
These large drums are also located in the drum tower. The drums used to be played every 2 hours, 24 hours per day, to signal the passage of time to the Bell tower:
The Bell Tower is about a block away from the Drum Tower, within hearing distance of the drums. The bell in the Bell Tower is rung after the drums are sounded, and the bell is loud enough to transmit the sound throughout the city. The tower itself is also designed to amplify the sound.
They no longer sound the drums and bell every 2 hours, but they do a very cool drum performance with 5 drummers about 6 times per day. It was incredibly loud but pretty amazing. The guide in the Bell Tower told us they only ring the bell a couple times per year now to preserve it, it is the second largest bell in the world. He also very proudly told us he got to ring the bell for Chinese New Years one year. On a side note, the Chinese people seem to be obsessed with measurements, every time we have a guide or read an informative sign, the first and sometimes only thing they tell you is how large or heavy something is. It's very odd.
After the drum and bell towers, we stopped in at a local espresso shop that is recommended in our Beijing guidebook. To this point, we had subsisted solely on jasmine green tea provided at our B&B, with an occasional Coke, for our caffeine needs. (On another side note, we have seen a Starbucks but did not try it.) Prices are comparable if not a little more expensive than in the USA. The barista said that he caters primarily to western tourists, that coffee is very slowly gaining popularity among Chinese, and that the Chinese favor sweeter drinks and/or tea. Well we bit, and I have to say, we were quite pleasantly surprised by the quality of our lattes - better I think than many US espresso joints, including Starbucks.