Apple has sent out the invites to its fall event, at which it is expected to launch the iPhone 6S. It will be held at the Bill Graham Civic Auditorium in San Francisco.

As ever, the invite teases what is due to be unveiled at the event. It makes no explicit mention of the iPhone but does suggest an update to Siri — its automated assistant — is coming.

The iPhone 6S is expected to look almost identical to its predecessor, the iPhone 6, and once again is expected to come in two sizes. Taking its queue from the Apple Watch, it is also rumored to include Force Touch, as well as a stronger grade of aluminum — the same Series 7000 aluminum also found in the Apple Watch.

After the iPhone 6 launched last year, there were a number of complaints that the device bent too easily under pressure, in what became known as "Bendgate."

There are also reports that the iPhone 6S will feature animated backgrounds as well as a smaller battery than its predecessor — suggesting increased efficiency.

Here's the official invite:

Here's what happens when you ask Siri about the event:

The Bill Graham Civic Auditorium is an interesting choice of venue. Apple normally holds its fall events at the Yerba Buena Center for the Arts, which hosts a relatively modest 755 people. In contrast, the Bill Graham Civic Auditorium has a maximum capacity of 7,000.