Like many of his compatriots, Russian Prime Minister Dmitry Medvedev enjoys combing the woods for mushrooms. And it was a photo of these delectables posted on Medvedev's Instagram page that opposition leader Aleksei Navalny used to help tie Medvedev to a lavish country estate shrouded in secrecy.

The investigation published on September 15 gives the wider public its first glimpse at the sprawling Volga River dacha complex in the Ivanovo region east of Moscow. For several years, the estate has been rumored to be a favorite weekend or holiday destination for Medvedev.

Citing geotags from an Instagram photo by Medvedev showing a basket full of mushrooms, Navalny placed the prime minister near the estate in the village of Plyos, where, according to earlier media reports, locals have wondered what lies behind a 6-meter-tall green fence on the perimeter of the complex.

Navalny and his team, who have published numerous investigations of senior officials' luxury real estate and other pricey assets, flew a drone over the estate. The video of the grounds caught its impressive amenities, including a large main residence, auxiliary homes, a cascading swimming pool, a downhill ski run and chair lift, and at least two helicopter pads.

A Novaya Gazeta investigation in 2011 showed that the property, known as the Milovka estate, was owned by an organization called DAR Foundation that, according to corporate records, specializes in "regional nonprofit projects."

DAR was founded by a firm owned by Russian billionaires Leonid Mikhelson and Leonid Simanovsky, and the head of its supervisory board was a former law-school classmate of Medvedev's, Novaya Gazeta reported. Simanovsky is a State Duma deputy from the ruling United Russia party.

According to Navalny, ownership of some of the Milovka estate's territory and buildings were later transferred to a nongovernmental "historical and cultural" preservation organization called Gradislava. A 2014 investigation by the Russian magazine Sobesednik linked Gradislava's founder to another expensive estate near Moscow that was allegedly owned by a firm whose founder had ties to DAR.

Following the publication of Navalny's investigation on September 15, Medvedev's spokeswoman, Natalya Timakova, confirmed that the prime minister had previously stayed at the Milovka estate on the banks of the Volga but that he did not own or rent the property.

Navalny responded to Timakova's remarks on Twitter by saying that if Medvedev had used the estate for free, "it's a clear case of bribery."

Navalny published his investigation just days ahead of federal parliamentary elections on September 18, in which he is calling on voters not to cast their ballots for United Russia.

Interestingly, the Instagram photo that helped buttress Navalny's investigation was dated September 15, 2013, exactly three years before his findings were published.

The caption on the Instagram photo is just one word: "Autumn...."