A report by the War Ministry led the celebrated Belgian military architect Henri Alexis Brialmont (who made several visits to Bucharest, meeting with King Carol in the process) to draft a plan for the city's fortifications, with construction beginning in 1884. The forts, about 4 km apart, cost 111.5 million gold lei (15 million were initially allocated), or three times the annual army budget. The forts took over two decades to build, and work was quite complex; the walls are two metres thick in places. All 18 were linked by a road and a railway, which today is DN100, Bucharest's ring road. 18 subterranean batteries were placed between the forts, and the fortification ring included some 240 pieces of artillery in all.