Bari is a university city that is also the hub of business and administrative business in Puglia. A gateway to Greece via boat ferry, the town has a bustling port and a fairly large metropolitan area of over a half million inhabitants. The city has many historically significant buildings and attractions, including the Basilica di San Nicola, St. Sabinus cathedral, Castello Normanno, the Russian Church and the Barivecchia, which is a sprawl of streets and passageways with two main squares, the Piazza Ferrarese and Piazza Mercantile. The city resides on the Adriatic sea and is considered the second largest economic centre of southern Italy. The climate is cool in the winter with summer temperatures averaging around 28º C.