Larger lizards pose larger problems when it comes to housing. Any custom enclosure is going to present custom problems in usable space, uvb/ir lighting, heating, humidity and cleaning. If this is an indoor enclosure it may require custom dimensions, and outdoor may be battling the weather, and one that can be moved from one to the other can severely limit the overalls size, weight, and water features.

Iguanas:

Young iguanas can be housed alone in some of the larger off the shelf 40-50 gallon enclosures or a 100 gallon melamine. But as an iguana reaches maturity they require much more space. At bare minimum, an adult will need 10ft by 5ft of floor space and at least 6ft of height to climb. 

The following enclosure is both indoor and outdoor connected by a passage way. Having an ability to block that passage and lock the iguana on the other side can make feeding, cleaning, and servicing much easier and safer. The is especially true when dealing with a pond and filter system.  There is ample climbing room that is not too steep and lots of places to bask. Large uvb lights and halogen basking lights would be positioned above the basking spots and protected by wire mesh to ensure the iguana cannot touch them. While the bark and logs are visually pleasing, if not sealed properly they my become difficult to clean. Also note how the water feature is raised up allowing the filter plumbing to be hidden blow. This also allows easier draining when you need to service the system.

Consider the following enclosure and how adding a raised pool at het bottom with a hidden filter system would make all the difference in how this enclosure both looks and functions. In this case the loss of real estate at the bottom to gain a large pool would be worth it. This would complicate feeding though, again, custom enclosures all come with custom problems to solve.

Lighting:

Recessed lighting is one of the safest ways to implement your fixtures as it is easy to screen to protect your inquisitive lizard. This also works for bar lights , you just need to cut a rectangular hole to match.  Make sure to engineer a way to easily get at your lights for bulb replacement. Also consider an extra amount of distance from the screen for high output lights like mercury vapor or Halogen lights so the wire doesn't get too hot.  Large enclosures require larger more powerful lights. I have found that large deep dome dimmable fixtures with build in rheostats (dimmer switches) are a low cost but highly effective way to implement halogen lights instead of your typical incandescent spot bulbs. The halogens can produce the same heat for half the power consumption and the dimmer switch allows you to control the resulting temp at the basking spot. Be careful to select a flood style halogen or spot bulb, some of the reflectors on non flood style beams can create intense hot spots at a distance like a magnifying glass which can burn your lizards skin.  Make sure to read up on UVB lighting for lizards on our site to understand the basics of distance and power of light before you commit to buying something as they are not cheap!

Below is a great example of a protected l;ight box with recessed lighting added to the inside of a custom enclosure.

This runs both a UVB light and Halogen light for daytime heat

Make sure to protect anything that is hot or can electrocute your lizard with the appropriate type of cage if your light or heater is not recessed. Industrial cages used to protect fire alarms at schools make good cages capable of holding up to the strength of a large reptile. The small cages often found at reptiles stores will not hold up to a large lizard at all.