In terms of overall dimensions and interior volume, the 2014 Toyota Sienna is one of the largest minivans you can buy, having grown slightly over its previous generation model. The revamped interior suffers a bit in richness; interior materials and appointments feel a bit less refined compared to those of its competitors, in particular the horizontal grain on the dash and door caps. You won't open a vein, but you will notice a difference if you compare it to Aunt Barb's '96 Camry.
In front, the Sienna has supportive, comfortable seats with lots of head and leg room. Most versions have standard power front seats, too.
The second row is where the Sienna distinguishes itself from most other minivans. The standard setup is a bench seat that slides to expand passenger or cargo space as needed. It also has a removable section that can be stored in the cargo area, to reveal a cupholder and tray--and space to walk through to the third-row seat. The second-row bench can also be swapped out for captain's chairs, or on the plushest models, lounge-style seats that recline like first-class airline chairs, down to the leg-cushion extenders and footrests.
Still, while it's possible to remove the second-row seats, they don't disappear into the floor. The Sienna is a reskin of the former model, and it wasn't designed to allow the middle seats to stow away in that way--a nifty trick formerly available on the Nissan Quest, and still offered in the utility champions, the Chrysler minivans.
The third-row seat actually has adult-sized room in all directions. It isn't that difficult to enter-and they fold almost flat into a deep well in the cargo area. With the second-row seats moved as far front as possible, the Sienna has 117.8 cubic feet of cargo room; with the second row removed and the third row folded, it will hold 150 cubic feet of cargo. Even behind the upright third-row seat, there's 39.1 cubic feet of space, almost twice as much storage room as the 2010 Ford Taurus' trunk. The Sienna also can carry an actual 4x8 sheet of plywood.
There's also plenty of small-item storage inside in the Sienna's console, twin gloveboxes, map and side pockets, and available cargo organizer.
By the numbers, the Sienna rides on a 119.3-inch wheelbase, and is 200.2 inches long overall, and 78.2 inches wide. Total interior cargo volume: it's 150 cubic feet. That's big.
That makes the Sienna an eight-passenger van with enough space for at least five adults, and a configurable cabin that has a fold-away third-row seat and a maneuverable second-row seat (or seats), though it lacks the fold-away second-row chairs found in Chrysler's minivans.