It is a long brick basilica (107 m) with a transept and a bypass around the presbytery. It was constructed in stages during the Romanesque and Romanesque – Gothic period (XIII c.) as well as in the Gothic period (the second half of XIV c.). The Oliwa Cathedral is perhaps best known for its massive, yet splendid rococo organ used in organ concerts during the summer season. The organ was constructed in 1763- 1788 by Jan Wulf of Orneta and finished by an organ master from Gdańsk Fryderyk Rudolf Dalitz. The organ is comprised of 7876 pipes made of oak, fir, pine wood and tin. Inside the cathedral there are 23 altars, mainly of great artistic value. They represent three architectural styles – renaissance, baroque (mainly) and rococo.