Pedra Branca) inside the Pedra Branca State Park. It has an altitude of 1024m. The Pedra Branca State Park (Parque Estadual da Pedra Branca) is the biggest urban state park in the world comprising 17 neighborhoods in the west side, being a "giant lung" in the city with trails, waterfalls and historic constructions like an old aqueduct in the Colônia Juliano Moreira in the neighborhood of Taquara and a dam in Camorim. Santa Cruz and Campo Grande Region have exhibited economic growth, mainly in the Campo Grande neighborhood. Industrial enterprises are being built in lower and lower middle class residential Santa Cruz, one of the largest and most populous of Rio de Janeiro's neighborhoods, most notably Ternium Brasil, a new steel mill with its own private docks on Sepetiba Bay, which is planned to be South America's largest steel works. A tunnel called Túnel da Grota Funda, opened in 2012, creating a public transit facility between Barra da Tijuca and Santa Cruz, lessening travel time to the region from other areas of Rio de Janeiro. International relations Twin towns – sister cities Rio de Janeiro is twinned with: Arganil, Portugal Atlanta, United States Baku, Azerbaijan Barcelona, Spain Beijing, China Beirut, Lebanon Braga, Portugal Buenos Aires, Argentina Busan, South Korea Cape Town, South Africa Casablanca, Morocco Cologne, Germany Guimarães, Portugal Guiyang, China Istanbul, Turkey Kyiv, Ukraine Kobe, Japan Lahore, Pakistan Lisbon, Portugal Liverpool, United Kingdom Luanda, Angola M'banza Congo, Angola Madrid, Spain Montpellier, France Nice, France Nairobi, Kenya Oklahoma City, United States Olhão, Portugal Ramat Gan, Israel Saint Petersburg, Russia Samarkand, Uzbekistan Santa Cruz de Tenerife, Spain Viana do Castelo, Portugal Viseu, Portugal Warsaw, Poland Partner cities Rio de Janeiro has the following partner/friendship cities: Berlin, Germany Kansas City, United States Moscow, Russia New York, United States Paris, France Philadelphia, United States Tokyo, Japan Toronto, Canada Yerevan, Armenia Union of Ibero-American Capital Cities Rio de Janeiro is a part of the Union of Ibero-American Capital Cities. Economy Rio de Janeiro has the second-largest GDP of any city in Brazil, surpassed only by São Paulo. According to the IBGE, it was approximately US$201 billion in 2008, equivalent to 5.1% of the national total. Taking into consideration the network of influence exerted by the urban metropolis (which covers 11.3% of the population), this share in GDP rises to 14.4%, according to a study released in October 2008 by the IBGE. Greater Rio de