For closed terrariums, imagine a rainforest floor environment. Speckled indirect light, shaded by the canopy of the trees. The glass amplifies the sun, so
If placed in bright direct sunlight it can cook the plants inside. It can also cause the temperature of the inside of the terrarium to rise so high, it encourages mold growth. In extreme circumstances it can also cause burnt leaves. So anywhere you could comfortably read a book during the day without turning the light on – that will be fine. It’s best to avoid rooms that are too hot/too cold as well. Never place near a turned on radiator. This can increase the temperature inside the terrarium, and can also heat the stones up causing the glass to crack! (Speaking from experience here….) Anywhere too cold can have the opposite effect, it can cause the glass to become very cold and any leaves near the edge of the glass can be shocked. This shock can ultimately travel down the roots and cause the whole plant to die. This will only happen in extreme circumstances, say, a very cold bathroom in winter!