Comparisons with the Arc de Triomphe may be a bit exaggerated, but the russet-red, newly restored Qing-era North Gate is rather photogenic, especially when it is illuminated at night. Originally constructed in the 1880s, it is the biggest of the city gates, through which the common folk could gain entry into the government quarter during imperial times.
The gate stands in the middle of Zhongxiao W Rd, just east of Zhonghua Rd. Take MRT Exit 2 and walk towards Zhongxiao W.
The area around the North Gate is home to several beautiful Japanese-era buildings including the Mitsui Warehouse, the Taipei Post Office and various railway offices. At the time of writing, apart from the warehouse and post office, these were all undergoing renovation, but it's worth checking if you're in the area to see if they've reopened.