|Ming Xiaoling, Nanjing City, Jiangsu||Hekeng Village, Nanjing County, Fujian|
Until recently, China's southeastern Fujian Province had much less of railway network than the country's other coastal provinces. This may have been partly due to the province's mountainous topography, partly due to strategic considerations (too close to Taiwan?). A few rail lines that existed in the province mostly followed zigzagging river valleys, connecting Fujian's coastal cities (Fuzhou, Quanzhou, Xiamen) with the nation's heartland.
In the 21st century the situation started to change. In April 2010, the coastal Fuxia (Fuzhou-Xiamen) Railway opened, connecting all major coastal cities of Fujian to each other and to the coastal cities further north (via Wenzhou, Ningbo, Hangzhou, and Shanghai). This coastal line is scheduled to be soon extended further southwest, all the way to Guangzhou.
In the mean time work started on high speed rail lines into the province's interior, cutting across mountains and valleys from the coastal cities to the inland centers. The first of them, the Longxia (Longyan-Xiamen) Railway opened on June 29, 2012. It may potentially become a convenient way of accessing Fujian's tulou country, as it will actually have a so-called Nanjing Station （南靖站), halfway between Zhangzhou and Longyan.
Now, this Nanjing is Nanjing County, Fujian (南靖), not to be confused with the better known Nanjing City, Jiangsu (南京)。The way maps show the new line, it actually runs through the eastern part of the county, so the station will be probably quite a ways to the east of Nanjing County's county seat (Shancheng Town), while most of the well-known tulou sites are some 30+ km to the west of Shancheng. Still, the new Nanjing Station is just 50 min from the centrally located Xiamen station, while getting to Nanjing County from Xiamen by bus may easily take close to 2 hours; so I have no doubts that some local transportation services between Nanjing Station and the touristy tulou area in the west of the county will become available soon.
Xiamen Railway Station now offers service both to Nanjing, Fujian (南靖) and to Nanjing, Jiangsu (南京). Make sure to get tickets to the right station!
Looking at the schedules, the new Longxia line will mostly have trains circulating between Longyan and Xiamen, as well as those continuing beyond Xiamen along the coastal line all the way to Fuzhou. Interestingly, there is actually one train coming to Fujian all the way from Nanjing, Jiangsu! It follows the newly built high-speed lines in a rather intricate pattern, tracing China's south-east coast: from Nanjing (Jiangsu) south-east to Shanghai, then southwest to Hangzhou, east to Ningbo, southwest to Wenzhou, Fuzhou, and Xiamen, and finally north-west to Nanjing (Fujian) and Longyan. According to the posted schedule, it takes 12 hours 15 minutes from Nanjing (Jiangsu) to Nanjing (Fujian), with 3 provincial-capital-level cities in between (Shanghai, Hangzhou, and Fuzhou). （For comparison, a "traditional" Nanjing-Xiamen train, taking an inland route, takes over 30 hours.)
With the travel time like this, it probably would have been a lot more practical if it were an overnight train, but, alas, very few high-speed (D-series) trains (and none of the fastest, G-series ones) in China operate at night, presumably because the authorities want to reserve the night time for safety inspection, maintenance, etc.