Chairman Mao is showing his age.

Lying in an open crystal casket encased in an airtight chamber at his massive mausoleum in Beijing’s Tiananmen Square, China’s former supreme ruler looks like a figure from Madame Tussaud’s wax museum. Surrounded by a bed of lilies, his body is dressed in his usual drab gray suit and draped in the Communist Party flag. His ashen face appears to have had more plastic surgery than Mickey Rourke.

That’s understandable considering that Chairman Mao has been dead for more than 37 years.

Pat and I got a brief glimpse of the Great Helmsman yesterday, joining a long line of visitors filing by the coffin at the Cold War-style mausoleum that was hurriedly built in less than a year following Mao’s death in 1976.

Security at the mausoleum is tight. You must show a picture ID, go through a metal detector and pass by a swarm of soldiers and guards before entering the building. No cameras, recording equipment or bags are allowed inside, though many Chinese visitors bring flowers that they leave at the entrance.

Outside the building are souvenir stands selling plates, busts, mugs, scrolls, lockets and keychains adorned with Mao’s image. If Mao had more room in that coffin, he would roll over in it.

Our guide told us that every so often they close the mausoleum for 3-4 weeks, supposedly for renovations. But when it reopens, she said, it’s hard to detect any changes. “We joke that they have done some plastic surgery on Chairman Mao,’’ she said.

We arrived in Beijing following an 11-hour, overnight train ride from Xi’an. Our private cabin had two sets of bunk beds, and our roommates were two college students returning home for the Spring Festival national holiday. One of them played “Braveheart’’ on his MacBook Air and we all watched it together before falling asleep. (Our guide says the train we took is known as the “Big Nose’’ because so many foreigners take it.)

After checking into our hotel, we headed to Tiananmen Square, site of the bloody 1989 pro-democracy demonstration that is rarely mentioned in China anymore. In the middle of the square is the Monument to the People’s Heroes, a 10-story obelisk dedicated to China’s revolutionary martyrs. Not far away, we saw a little girl squatting and peeing as her mom held her hand. Children doing their business in public is a common sight in China, though it’s relatively rare in big cities like Beijing and Shanghai.

We then visited the Forbidden City, home of China’s emperors for almost 500 years. Bernardo Bertolucci’s Oscar-winning 1987 movie, “The Last Emperor,’’ was mostly filmed in the Forbidden City. When Pat and I watched it that night in our hotel room, we kept pointing out the places we had seen earlier in the day.

In the afternoon, we took a rickshaw ride through the city’s largest hutong neighborhood, a labyrinth of narrow alleys lined with brick walls and the front doors to small courtyard homes built centuries ago. Our guide took us inside one three-room hutong, where the retired couple who lived there served us a tasty lunch of rice, shredded potatoes, diced chicken, fried dumplings, scrambled eggs and green beans with pork. (Many retired couples host lunches for tourists to make some extra money.)

Our last stop was the city’s Drum Tower, which was once used to signal the time of day. We climbed 69 steps to the top, where we watched a ceremonial performance by five men beating on huge drums with small wooden sticks. The tower also has an exhibition of ancient timekeeping methods, including burning candles, incense and oil.

It was getting late, so I glanced at my digital watch and noticed it had stopped. So much for progress.