Only once, and it wasn't planned. We were on a flight to Nairobi, across the Indian Ocean, back in the 70s. The plane was badly damaged in a severe tropical storm and had to divert to Sri Lanka, and we spent two days there waiting for the airline to fly in a replacement aircraft, as their local resources couldn't repair the first one quickly.
I remember it was very, very, hot. Probably 40C or more. We went for a walk around Colombo and something that sticks in my mind are the old, decaying, abandoned colonial era buildings. Some of them were covered in creepers and other vegetation, growing wild, and a few had trees growing right through them. Sri Lanka is very fertile, hot and gets a lot of rain during the monsoon season, so I suppose nature takes over pretty quickly when it get a chance.
That was more than 30 years ago and they may have gone now, or been refurbished, but it was pretty evocative at the time. Might be worth a look?