[3][4] In October 1980, Alttoa was a signatory of the Letter of 40 Intellectuals, a public letter in which forty prominent Estonian intellectuals defended the Estonian language and protested the Russification policies of the Kremlin in Estonia.
[5] The signatories also expressed their unease against Republic-level government in harshly dealing with youth protests in Tallinn that were sparked a week earlier due to the banning of a public performance of the punk rock band Propeller.
[5] Alttoa has mainly studied the medieval architecture of Estonia, such as forts and sacral buildings.
In 1995, while working at the university, he completed his master's thesis on medieval brick buildings in southern Estonia.
He was also one of the editors of the Castella Maris Baltici series publishing international bird surveys.