The Tunguska event occurred at a remote time in a remote place. This fact has served both to add mystery to the story, and to frustrate those interested in knowing what happened.
The explosion was centered in the middle of Siberia, some 1000 km northwest of Lake Baikal (the largest freshwater lake in the world).
To reach the site, one could start from the Imperial capital of St Petersburg, taking the overnight train to Moscow.
From Moscow, one would board the still-new Trans-Siberian Railroad, leaving again in the evening, heading east towards the Urals, through Ekaterinaburg (where the Tsar and his family would be killed by the Bolsheviks), then skirting the edge of Kazakhstan, through Novosibirsk, then Krasnoyarsk, then to the town of Tayshet.
This town is at the 'shoulder' of the curve where the railroad turns to the southeast, to Irkustk and Lake Baikal.
From Tayshet, then, one must hire teamsters: horse-drawn sledges would provide the best transport over still-primitive roads.
Head north-east, passing well-west of Bratsk, and after 500 km or so, one would reach the town (although that would be a generous description) of Vanavara.
Vanavara lies about 70 km to the southeast of the Tunguska site. This is a small settlement with a trading post, and really the closest developed area to the site.
From here, one would need to speak with the indigenous people, the Tungus (now known as the Evenks), for guidance on reaching the blast centre.
This area of Siberia is still unpopulated and undeveloped in 1908. The Tungus people live as reindeer herders, maintaining a semi-nomadic culture in the forest. The western settlers are here as hunters and trappers and such, or here to escape the reach of the Tsar's empire.
After the "reforms" of the church in 1652 by Patriarch Nikon, the so-called Old Believers who did not support the changes were exiled to Siberia. A number of these staroobryadtsy ("old ritualists") lived in the area. (Due to a difference in how times of the day were called by the Old Believers -- compare our uses of "dinner" and "supper" in English -- their testimonies about the disaster would be called inconsistent with those of the other population.)
The wilderness around the Tunguska site is made up of taiga forest, a sub-arctic type of biome consisting of coniferous trees, and only the hardiest of deciduous trees, e.g. spruce, larch. The forest is dense, and the ground cover is moss and lichen. A forest fire, started by lightning, had destroyed a considerable area about one hundred years prior, and most of the trees that would be claimed in the blast would be only 100 years old.
The Tungus tribe gave its name to two rivers in the area, tributaries of the great Yenisei which flows north into the Arctic Ocean: the Nizhnyaya ("Lower") Tunguska and Podkamennaya ("Stony") Tunguska rivers. "Stony" is the usual English translation, but it literally means "under-stone", as the river flows under pebbles for part of its course. The Stony Tunguska is the closest to the blast site.
What would become the epicentre is a swamp; the first expedition to the site in 1927 would label them the Northern and Southern Swamps. Flies and mosquitoes form large clouds over the swamps during the short-but-hot summers. Other wildlife in the region are reindeer (a herd of 700 or so kept by the tribesmen), bears, turkeys, and smaller forest mammals.
The Tungus practice a animistic/naturalistic polytheistic religion. The loan-word "shaman" comes from their language, and coincidentally, a shaman of one of the local tribes would be blamed (or lauded, depending on which tribe was doing the talking) for the blast, having called down the wrath of Agdy, the god of thunder.
By all accounts, the morning of June 30 was clear, hot, and dry. There were no clouds in the skies over most of the region. It was a Tuesday; by the old-style Julian calendar, it was the 17th of June, one week before the feast of the nativity of St John the Forerunner for the Orthodox, and close to the summer solstice for the Tungus' native religion.
What happened next was otherworldly: at 7:14 AM local time, an explosion occurred near 60 degrees north latitude and 101 degrees east longitude, destroying some 10,000 square kilometres of forest.