The tomb of Sultan Mahmud II (reg. 1808-1839) was built in 1840 by the sultan's son Abdulmecid. The mausoleum was constructed in the then-popular Ottoman Empire style, one influenced by the neoclassical, Napoleonic French Empire style.
The tombs of Sultans Abdulhamid II and Abdulaziz are also contained within the same compound.
Sources:
Oleg Grabar, et al. "Islamic Art." In Grove Art Online. Oxford Art Online,
http://www.oxfordartonline.com/subscriber/article/grove/art/T041771pg10 (accessed September 20, 2010).