30 days entry visa to Sri Lanka could be either obtained online or paid and received on arrival.
These Visas could be normally extended to three months after which provided that if you meet any specific requirements.
Three types of Visas are in force in Sri Lanka, namely Investment (If you intend to live in Sri Lanka you will probably want to consider investing $250,000 US in the country. Either through the BOI (Board of Investment) or similar department), Resident Guest (If you have a particular skill or qualification that can be shown to be of material or cultural benefit to the country) and Retirement (If you are over 55 and wish to retire here, under a special programme named ‘Sri Lanka- My dream home’ you can apply. It is much cheaper than the investment route).
Longer term visas can run from one to five years and it is even possible to apply for citizenship after three years.