So high are its peaks in some places that certain areas are accessible only by helicopter. The republic is also famed for its ethnic and linguistic diversity, being home to more than 30 languages.
Several dozen Muslim peoples have settled among the high valleys over the centuries.
The Avars form the largest ethnic group and account for about a fifth of the population. A further substantial proportion is made up of Dargins, Kumyks and Lezgins. About 10 per cent are ethnic Russians. There are also Laks, Tabasarans and Nogai, to name but a few of the other significant groups.
At A Glance
Politics: Dagestan's politics is dominated by the need to balance its many ethnic groups. A long-running militant Islamist insurgency is a thorn in the authorities' side
Economics: Dagestan has oil reserves and a strong manufacturing sector, but rampant corruption and organised crime hold back growth
The republic's constitution declares the protection of the interests of all of Dagestan's peoples to be a fundamental principle. It is a delicate balance to maintain, in what is Russia's most ethnically diverse province.
The republic has oil and gas reserves and also the fisheries potential offered by a share in the resources of the Caspian Sea. However, it is prey to organized crime and regional instability. The crime barons may prosper but the people are amongst the poorest in Russia.
Dagestan was the birth place of Imam Shamil, the legendary fighter who in the 19th century spearheaded fierce resistance by tribesmen of Chechnya and Dagestan to the spread of the Russian empire. His name is still revered by many in both republics.
Federal troops were deployed to repel incursions by Chechen militants in the 1990s
When the Bolsheviks sought to enforce control in the Caucasus in the early 1920s, Dagestan became an autonomous Soviet republic within the Russian Federation. During the Stalinist period, its peoples escaped the mass deportation inflicted on their Chechen neighbours and many others.
After the fall of the Soviet Union, the republic's authorities stayed loyal to Russia, but the region became infamous for its lawlessness and corruption. Organised crime is reported to flourish and kidnappings and violence are commonplace. Firearms are ubiquitous and assassinations are a regular event.
Moscow blames much of this on Chechen-based separatism, but others say lust for profit, combined with a gun culture, is the root cause.
Budennovsk and beyond
In the 1990s, separatist warlords from neighbouring Chechen openly led armed operations in Dagestan on several occasions. In 1995 and 1996, they seized hundreds of hostages in hospitals in the Dagestani towns of Budennovsk and Kizlyar. Scores died in the attacks.
Dagestan's Muslims, who tend to follow sufism combined with local tradition, generally steered clear of Chechen-style separatism, but after the late 1990s, radical and militant elements said to be linked with the more fundamentalist wahhabist tendency began to gain in influence.
In August 1999, an Islamic body declared an independent state in parts of Dagestan and Chechnya, and called on Muslims to take up arms against Russia in a holy war.
Chechen fighters crossed into Dagestan in support, but within a few weeks, Russian forces had suppressed the insurrection.
The republic has seen numerous bombings targeted at the Russian military stationed in the republic.
Russia accused Dagestani militant Magomed Vagabov of being behind an attack on the Moscow metro by two female suicide bombers from Dagestan in March 2010, in which 39 people died. In August 2010, Russian forces killed Vagabov in Dagestan
1) What are Chechnya and Dagestan?
The most basic answer is that they're two federal subdivisions of Russia, both in the country's far southwest. They're small, mountainous, predominantly Muslim and have been marked by years of conflict and independence movements.
The regions are known for their diversity and scenic beauty, but they've also sadly become famous as flashpoints of internal Russian conflict.
2) Why is there conflict in Chechnya and Dagestan?
To understand that you have to know that it's been almost 200 years since they were independent. In the early 1800s, Russian Tzar Nicholas I led an invasion of the Caucasus, including the regions we now know as Chechnya and Dagestan. After decades of fighting, they were incorporated into Imperial Russia, and have been under some form of Russian rule ever since.
Chechnya, and to a lesser extent Dagestan, have periodically rebelled against Moscow in a sometimes-violent effort to secure independence. Some of this violence has been led by separatists and some by "jihadists" who profess an extreme version of Islam. Some of it has been directed at local, pro-Moscow governments, some of it at people in Moscow itself and, during some of the worst years after the fall of the Soviet Union, against Russian troops sent to the region to put down the uprisings.
3) Was There A War in the 1990s?
Two wars, actually. The First Chechen War began in 1994. A few years earlier, when the Soviet Union dissolved and its various regions either seceded or negotiated their place in the new Russian Federation, Moscow's talks with Chechen representatives fell apart. Nationalist movements had been gaining momentum in Chechnya for years, some of them armed, and in 1991 a former Soviet Air Force general maneuvered his way into becoming the president of Chechnya, after which he quickly declared independence. Three years later, Russia sent tens of thousands of troops to invade and retake Chechnya.
The First Chechen War, which lasted almost two years, was brutal: Fighting claimed thousands of lives, including many civilians. Chechen groups devolved into insurgencies; Russian troops were accused by human rights groups of summarily executing men in their homes, firing deliberately into civilian areas and, according to one Human Rights Watch report, leading a "massacre" in the town of Samashki that the United Nations says ended in more than 100 civilian deaths. Eventually, Russia retook Chechnya.
The first war and its aftermath, according to a report by the International Crisis Group, "transformed the nationalist cause into an Islamist one, with a jihadi component." Jihadist groups started to rise in influence and, in 1999, a Chechnya-based group invaded the neighboring Russian region of Dagestan. They seized several villages, declared war against Moscow and said Dagestan was now an independent Islamic state. Once again, Russian troops moved in.
The Second Chechen War, like the first, took thousands of lives, including many civilians, leveled wide swathes of the country and was marked by allegations of horrific human rights abuses on both sides. Though the war lasted less than a year, it bled into neighboring Dagestan, as did the decade of insurgency and military presence that followed.
4)Is The War Over Now?
Not really, no. Low-level rebel violence persists in the region, according to the Crisis Group, and Chechnya is now run by a leader known for his allegiance to Moscow, consolidation of power and sometimes severe crackdowns, none of which have exactly dispelled the underlying issues that led to the wars in the first place. Jihadist groups continue to operate there.
Dagestan has never had quite as tough a time as Chechnya, but it has struggled with insecurity and violence, which scaled up significantly in 2010.
The violence and extremism have spread beyond Chechnya and Dagestan. In 2002, fighters who claimed to represent Islamist Chechen separatists seized a crowded theater in Moscow, taking hundreds of civilians hostage. In a microcosm of the larger conflict, Russian forces responded by pumping the theatre full of a toxic gas that killed 130 of the hostages. All of the militants were killed. In 2010, two women believed to be Chechen Islamist rebels bombed the Moscow subway, killing 40.
Depending on who you ask, the reason for the violence has either changed dramatically over the past 200 years, swaying from separatism to nationalism to Islamism to general lawlessness, or it's been part of a consistent struggle to break free from Moscow's rule.
It's hard to separate the two, particularly given Chechnya's and Dagestan's long and traumatic histories with Moscow. After Chechen insurgents tried and failed to win independence during World War II, for example, Joseph Stalin approved a plan to forcibly relocate more than 400,000 Chechens, sprinkling them throughout the vast Soviet Union and undermining the very idea of a distinct Chechen identity. (Some of them ended up in Kyrgyzstan, which may explain why one of the Tsarnaevs was reportedly born there.) And that 1940's rebellion was itself a partial response to Imperial Russia's deportation of 100,000 Chechens a generation earlier.
7) So whom do we blame for the violence? Is it Moscow or Jihadists?
It's not that simple. First of all, whatever the Boston Marathon suspects believed and whomever they blamed, the Caucasus conflict has too complicated a history to be pinned on any one group or ideology.
One writer has called the conflict with Moscow "a circular pattern of marginalisation, violent rebellion, and deportation that consumed the peoples of the North Caucasus."
A second Crisis Group report, calling the Caucasus conflict the most violent in Europe, explained, "The root causes of violence are as much about ethnicity, state capacity and the region’s poor integration into Russia as about religion."
It's about identity, about law and order or its absence. It's about the still-unresolved questions about Chechnya and Dagestan's place within but still distinct from the larger Russian state. It's really, really complicated.
8) Are things improving in Chechnya and Dagestan at all?
Things are not nearly as bad as they were a decade ago but, as the Crisis Group warned in its two 2012 reports that militant attacks are still a regular part of life, often against police or government targets; jihadist groups still operate in small numbers in the region; and, of course, the 2010 Moscow subway bombing was only three years ago. Neither the regional governments nor Moscow appear to be trying to solve the underlying issues so much as tamp down the extremism and violence.
This line from the second Crisis Group report is almost haunting in its potential prescience: "These harsh measures [by the Russian and Caucasus governments] do little to convince radicalised parts of the population to give their allegiance to the Russian state. They seem instead to stimulate a new generation of disillusioned youth to 'join the forest' (go over to the insurgency) in search of revenge or a different political order."
9) What's The Big Takeaway?
The conflict in Chechnya and Dagestan is relatively quiet right now, but has been ongoing in some form or another for almost 200 years.
The issues at the heart of the conflict remain: Chechens and other peoples in the Caucasus region are struggling to retain an identity distinct from the larger Russian mass; Moscow and the pro-Moscow government in Chechnya are working to tamp down extremism and violence rather than address the underlying grievances; extremism and jihadism are filling the void left by two awful wars in the 1990s; and young people feel dispossessed and prosperity has not really arrived.
None of this necessarily means that the Chechen and Dagestan conflicts will define or "explain" what happened at the Boston Marathon, but as more biographical details emerge linking these two young suspects to a restive and little-understood part of the world, it can't hurt to better understand what's happening there and why it's been so troubled.