early 1990s, Groningen used various permutations of green and white on their home kits, when the club adopted a white shirt with two vertical green stripes. Stadium The side have played their home matches at Euroborg since January 2006, which replaced Oosterparkstadion, the home of GVAV and Groningen since the 1930s. The Dutch national team played two international matches at Oosterparkstadion: against Cyprus in 1981 and in 1983 against Iceland. In 1985, Groningen recorded their largest attendance at the stadium in a 1–1 draw against Feyenoord, when 21,500 spectators attended. The club first expressed an interest in building a new stadium away from Oosterparkstadion in 1996 as it had become outdated and had only a capacity of around 12,500. In 2003, Groningen started with the building of Euroborg; Wiel Arets was the architect. The stadium was opened on 13 January 2006 with a match against Heerenveen, which Groningen won 2–0. It hosted the 2007 UEFA European Under-21 Championship final, in which the Netherlands defeated Serbia 4–1. In 2014, Groningen became the first Dutch club to have its own solar power plant; more than 1,000 solar panels were placed on the roof of Euroborg to make Groningen "more eco-friendly". Euroborg's current capacity is 22,525, and is nicknamed "De Groene Hel" ("The Green Hell") and "De Groene Kathedraal" ("The Green Cathedral"). The stadium consists of four stands: the Tonny van Leeuwen Tribune, the Piet Fransen Tribune, the Koeman Familie Tribune and a stand containing skyboxes. Supporters and rivalries Groningen's supporters are mainly drawn from the provinces of Groningen and Drenthe. During their early years, Groningen also had a decent following in Friesland as they were the only Northern team in the Eredivisie, which earned them the nickname "Trots van het Noorden" ("Pride of the North"). During 1979–80, when the team won the Eerste Divisie title, a ultras group known as the Z-side emerged from within Groningen's fanbase. The Z-side and other Groningen ultras groups have had long-standing friendships with the ultras and hooligans of A.S. Roma, Beerschot and Rot-Weiß Erfurt. In 1984, a Groningen supporters' association was formed. As Groningen are one of the few professional sides in the Northern Netherlands and the only team from the province of Groningen, the team lack rivalries. Until SC Veendam was dissolved in 2013, Groningen contested the with the club. The sides met only four times in the Eredivisie—in 1986–87 and 1988–89, with both teams