The Assembly, Integration and Verification room for large instruments (AIV) is an infrastructure of common use for the assembly and testing of instruments that, due to their size characteristics, require large spaces and cleanliness conditions. Internally this room is divided into three areas: storage, rotators, and laboratory, all with a height of 10m. The laboratory zone has an area of 125 m2 and in it there is a bench, with independent foundations from the rest of the building to avoid external vibrations, of 10x1.2 m2 with a rectangle of 2.5x2.3 m2 in the center. This bench allows for high stability optical setups and testing. The cleanliness level of the room is class 8 and it has controlled temperature and humidity. The rotators zone has an area of 220.5 m2 and in it there are two independent benches of 8x7 m2 isolated from the rest of the building. In one of them it is installed a simulator of the rotator of the Nasmyth focus of the Gran Telescopio Canarias (GTC). This infrastructure is used to verify the correct coupling of the instruments prior to their transfer to GTC and, above all, to verify that their behavior against the rotation that is going to occur in the telescope during the observation, is correct, that is to say, undesired flexures or misalignments that affect the quality of the image are not produced. This area, like the laboratory, has a cleanliness level of class 8 and its temperature and humidity are controlled. The storage zone is an area of 154.5 m2 and besides serving as a general purpose warehouse, also houses an aluminizing plant. All areas have a height of 10m and there are bridge cranes of 8 tons to transfer of loads from one room to another. The floor of the laboratory and rotator zones has a network of manholes communicated with each other and also communicated with electrical panels, compressed air outlets, refrigeration circuit, telephony and data, in order to carry all these services to any part of these areas underground. In the whole room there is three-phase, single-phase and uninterrupted power supply, and there is a generator that guarantees the electrical supply in the event of failures or cuts off for maintenance. The AIV room and part of its equipment has been funded by ERDF.