After 14 years of construction, court battles, and one of India's most contentious tree-felling controversies, Mumbai Metro Line 3 opened in October 2024 — the financial capital's first underground metro, connecting Aarey Colony to Bandra-Kurla Complex beneath a city that had almost given up believing it would ever arrive.
Mumbai is a city that runs on time — or tries to. Its suburban railway, a network of three overcrowded lines carrying more than seven million passengers a day, is the circulatory system of the metropolis. For decades, that system was also the city's ceiling: fast and extensive for the inner suburbs, but largely inaccessible to the central business district without a chaotic last-mile transfer. A metro line had been proposed, studied, delayed, and redesigned so many times that many Mumbaikars had quietly stopped expecting it.
On 7 October 2024, Prime Minister Narendra Modi inaugurated Phase 1 of Mumbai Metro Line 3 — the Aqua Line — between Aarey Colony in the north and Bandra-Kurla Complex (BKC) in the south. It was, depending on how you counted, fourteen years in the making.
The line that had to go underground
Mumbai's existing metro lines — Line 1 (Versova–Andheri–Ghatkopar) and Line 2 (Dahisar–DN Nagar) — are elevated. Line 3 could not be. Its route cuts through some of the most densely built parts of the city: the former mill lands of Lower Parel, the government and financial hub of Nariman Point, and the legal district around the Bombay High Court. Acquiring surface land was impossible; elevated structures would have collided with heritage buildings and arterial roads. The line had to go underground, making it the first fully underground metro in Mumbai.
The Mumbai Metro Rail Corporation (MMRCL) was established in 2009 to build it. Tunnelling began in earnest around 2016, using tunnel boring machines imported from Europe and Japan. The geology beneath Mumbai — a mix of rock, reclaimed land, and groundwater — was demanding. Engineers encountered underwater springs in the Lower Parel section and had to reinforce foundations to protect colonial-era structures above.
Aarey: a forest, a controversy, and a compromise
Nothing about Line 3 generated more heat than its northern terminus. MMRCL chose Aarey Colony — a 1,287-hectare green buffer zone in the northern suburbs — to house the metro car shed, a maintenance and storage facility for the rolling stock. Aarey contains patches of forest used by leopards, tribal communities, and migratory birds. When MMRCL received clearance to fell approximately 2,700 trees for the car shed in 2019, protests erupted across the city. Activists chained themselves to trees. Students camped at the site. Courts received multiple petitions.
The Supreme Court stayed the felling temporarily, but the trees came down in a single overnight operation that sparked outrage. The issue became a flashpoint in the 2019 Maharashtra state elections. A subsequent government briefly proposed relocating the car shed; the plan was eventually abandoned, and MMRCL proceeded with Aarey. The controversy did not stop the line — but it permanently attached a moral cost to the project in public memory.
Bandra-Kurla Complex: the destination that made the project worth it
BKC — Bandra-Kurla Complex — is where Mumbai's financial gravity shifted in the 1990s as the old Nariman Point business district became congested. The headquarters of major banks, the SEBI regulator, luxury hotels, and the American and British consulates are all in BKC. It is also notoriously hard to reach. Auto-rickshaws are banned in the area; taxis queue in long lines; the nearest suburban rail stations require a bus or auto transfer. For years, BKC workers spent 45 minutes to an hour simply getting from the train to the office.
Metro Line 3 changes that calculation. The BKC station gives direct underground access to the financial hub from Aarey to the north and — when Phase 2 is complete — from Cuffe Parade at the southern tip of the island city. Office workers who once took a suburban train to Bandra and then a bus into BKC can now change to the metro at Western Line stations and arrive at BKC in a single ride.
What Phase 1 covers and what comes next
Phase 1, inaugurated in October 2024, connects Aarey Colony to BKC with stations at major points including Andheri, Marol Naka, SEEPZ, Airport Road, and Santacruz. The full Line 3 corridor extends southward to Cuffe Parade — a total of 33.5 kilometres with 27 stations, making it one of the longest underground metro lines in India.
Phase 2 (BKC to Cuffe Parade) passes through Worli, Haji Ali, Mahalaxmi, Vidhan Bhavan, and Churchgate — the commercial and cultural spine of south Mumbai — before terminating at Cuffe Parade, near the Navy Nagar area. When Phase 2 opens, the Aqua Line will offer a single underground journey from the suburban fringe to the southern tip of the island, a commute that previously involved three transfers and an hour in traffic.
What Mumbai's metro means for Bengaluru
The Aqua Line's travails — a 14-year construction timeline, cost overruns, legal challenges, and the Aarey controversy — are a reminder that building urban infrastructure in dense Indian cities is rarely straightforward. Bengaluru Metro (Namma Metro) has its own version of this story: Phase 2 extensions involved elevated sections across residential neighbourhoods, heritage objections, and tunnel boring through Bengaluru's hard granite.
But the shared lesson is that metros do get built, and when they do, they reshape city geographies in ways that traffic planners can rarely predict. BKC went from Mumbai's most annoying commute to its most metro-accessible in a single year. For Bengaluru, which is extending metro lines to Whitefield, Bommasandra, and eventually the airport, that precedent matters.