China, even after almost 35 years, can still be a learning experience, with situations or approaches fundamentally different from what I was familiar with back in Scotland. Consider 1992, I was based at an excellent educational establishment in suburban Guangzhou. As a geographer, I was very familiar with maps. Naturally I was curious about how different were the world charts I was seeing on classroom walls. China was at the center, while those I was familiar with in Scotland were based on the Mercator Projection, placing Europe and Africa in the middle. I was intrigued, fascinated with this different concept of position or place.

Chinese friends introduced me to the characters 中国 and the pinyin, zhong guo. They explained how this translates into Middle Kingdom (or country). How it also reflects a perception of China's several thousand years of history and evolution of civilization. Knowing something of this I believe is essential toward a deeper understanding of China today.

So how does this translate into my ongoing passion for Beijing? It comes from having a curiosity derived from an academic background in historic geography.

My first visit, to the capital, in 1987 was short, mainly taking in grand architectural masterpieces dating back to the Ming Dynasty (1368-1644). Seven years later, in 1994, I returned to Beijing, staying in a hutong alley near Yonghegong (Lama Temple). Walking daily, I started to appreciate a pattern, a certain order regarding the orientation of alleys, the location and layout of dwellings such as traditional siheyuan courtyard homes. It was fascinating, but what of the story and history of the city, why did some of it appear as almost a chessboard pattern?

With no online search possible at that time, I would look closely at any street maps I could find while also searching through the shelves at Beijing Foreign Languages Bookstore on Wangfujing. Gradually my thoughts started to coalesce about how historic Beijing was constructed around a master plan that envisaged a central axis line at its heart. Again I started appreciating the character 中 (zhong) and whether the vertical stroke could be a central axis with the frame representing China. I was also coming upon this concept in some academic writing. As I looked closely at historic maps, it became apparent how the early city had been laid out to follow this in many ways.

Beijing for me was like slowly reading and turning over the pages of a book to discover more.

I realized how physical geography helped explain some of its early history and construction. Looking north, a relatively narrow range of mountains marks the border, indeed an interface between fertile, arable lands to the south with much drier terrain beyond. The Great Wall acted as a defensive barrier between the two. The northern lands, initially grasslands giving way to deserts such as the Gobi, were inhabited mainly by semi-nomadic pastoralists. To the south, more humid conditions created the possibility of arable cultivation and ultimately an urban-based society. Several of the world's oldest cities are in China.

The Great Wall, a mainly Ming Dynasty (1368-1664) defensive structure, stood against incursions from the north. However, long before the Wall was constructed, the threat of invasion was real. Hence the massive walls and moats that were constructed around urban settlements such as Beijing.

Beijing has occupied its present location since 1271. A succession of earlier cities had been built relatively close to the present city, though succumbing to the invasions and turmoil of those earlier periods in history. The historic precursor to present-day Beijing's site was Zhongdu, located close to Fengtai district. Indeed ongoing construction of the impressive Lize Financial Business District is where once there was a city gate of that name, Lize.

Zhongdu was capital of the Jin Dynasty (1115-1234), but by 1215 attacked and destroyed by the northern invaders.

By 1271, a new city, Dadu, located slightly northeast of Zhongdu, was declared capital of the Yuan Dynasty (1271-1368).

Lasting only 97 years, the Yuan did lay the foundations for present-day Beijing. Some of the city's older alleys can trace their origins to that period.

Dadu would be built in harmony with an axis line (zhong zhou xian 中 轴 线 ）initially 3.7 kilometers long, which would epitomize the importance of the center, or zhong. Over subsequent years, this philosophy would continue being applied toward the city's layout.  It was to represent  the concept of center or middle of the country. The line to stand as a backbone of the city, reflecting precision, symmetry. The city to be laid out in harmony with the axis.

In 1368, the Yuan was unseated by the Ming, who continued to rule until 1644. Initially the capital was relocated south to Nanjing. However, by 1421, Ming Emperor Yongle had reinstated Beijing as the capital.

The northern section of former Yuan Dadu was abandoned. A much stronger city wall would run  roughly along the line of today's No 2 metro line. Eventually, an outer city wall was constructed that included Yongdingmen Gate, built in 1553. It became the southerly point of a by-then 7.8 kilometer axis.

The Ming represented a construction period for some of China's finest historic architecture. The Axis Line acting as a meridian, along which  much of that early city would be laid out in symmetry.

The axis, going through the core area of the historic city of Beijing, is the longest urban central axis still existing in the world.

Forbidden City, constructed 1406-1420, sits exactly on the axis, representing its position then at the center of the Middle Kingdom. The Dragon Throne (longyi) within the palace's premier structure, the Hall of Supreme Harmony, straddles the line.

Referred to as Imperial Way, only the emperor could walk along the axis, although during ceremonial occasions, he would be carried in a highly ornate chair.

Located in harmony with the palace, but beyond the city walls, sit the Altars of Sun (ritan) to the east, Moon (yuetan) to the west, and Earth (ditan) to the north. In the south, close to Yongdingmen, are Temples of Heaven (tiantan) to the east and Agriculture (xiannongtan) to the west.

The axis was not simply about the Imperial Court residing within Forbidden City. Beijing was of course a city of people. Apart from many royal officials, who often lived in grand courtyards, there were also the ordinary citizens. Shopkeepers, porters, teachers, security guards and so many more. They filled essential roles for keeping the city functioning.

The axis line reflects many aspects of historic Beijing. Walking its length presents a fascinating insight into how the early city operated. One of my favorite areas, at the very north of the axis, is Zhonggulou, where the iconic Bell and Drum towers still stand. Once the tallest structures within the city walls, they would hourly chime out the time - people then did not have clocks or watches! They also indicated when the city's gates should close at night.

The view from the Drum Tower is south along Di'anmen Outer Street. It once was the early commercial heart of the city, for it is located adjacent to Qianhai, one of Shichahai's several lakes. Presently very busy with winter outdoor skating, it was once a bustling harbor for boats bringing supplies north along the Grand Canal from Hangzhou. Indeed, the Jade River (yuhe) crossed by historic Wanning Bridge was the actual waterway connection into Shichahai.

South of that bridge once stood Di'anmen (Earth Gate), the northern entrance to former Imperial City with Jingshan Park and hills beyond. Jingshan, made up apparently of rubble retrieved from excavation of a moat around Forbidden City, is an outstanding viewpoint along the axis. Looking north is toward the historic towers of Zhonggulou, but south represents a stunning panorama along the axis of Forbidden City. The harmony of its layout is clearly visible.

The axis continues, passing through the palace's southern entrance, Meridian Gate, also known as Wumen. Beyond, Tiananmen Gate is one of the most instantly recognizable icons of historic Beijing. It is the southern entrance into Imperial City, with the axis, of course, connecting it with Forbidden City. The view from its podium clearly shows the axis heading south along Tiananmen Square. Along that line once stood many important buildings and offices of both Ming and Qing dynasties. Beyond rise the magnificent towers of Zhengyangmen and Jianlou, part of Qianmen, the front gate of the Inner City.

Qianmen Street, I remember clearly the earlier days when it was a busy thoroughfare with many buses, with little feeling of its easier vibrancy and historic importance. During the Qing Dynasty and into the early 20th century, it had become the main commercial hub of the city. However, Dashilar, running west from Qianmen, has even today retained much of its feeling from the days of Old Beijing. Since 2008, Qianmen has changed considerably, with pedestrianization and upgrading, the iconic Axis Line once again visible, the area now a popular tourist destination. Qianmen continues south toward Zhushikou and Tianqiao, the latter once a vibrant hub of traditional Beijing culture.

Finally a broad park-lined avenue heads straight toward Yongdingmen Gate, which once controlled access to the city from the south. The Temple of Heaven a major icon, close by.

Beijing today may appear increasingly as a dazzling, high-rise modern city. However, at its core is a unique example of historic urban design based around an axis line reflecting its location at the heart of China.