Since Black's third move does not threaten to win the e-pawn—if Black captures it, White will win back the pawn on e5—White usually castles. After 4.0-0, Black can play either the solid 4...Nxe4 (the Berlin Main Variation) or the more combative 4...Bc5 (the Berlin Classical Variation). After 4...Nxe4 5.d4 Nd6 (5...Be7 is the Rio de Janeiro Variation) 6.Bxc6 dxc6 7.dxe5 Nf5 8.Qxd8+ Kxd8 (l'Hermet Variation), White is considered to have a small advantage from a somewhat better pawn structure and Black's awkwardly placed king. Black, by way of compensation, possesses the and has no positional weaknesses, so it is difficult for White to exploit the structural superiority without opening the game for Black's bishops; all four of the games in the Kasparov–Kramnik match in which this line was employed ended in draws. An alternative for Black, though seldom seen since the 1890s, is 6...bxc6 7.dxe5 Nb7, although White keeps an advantage despite Black's two bishops, as it is difficult for him to gain active . However, despite its drawish tendency, the Berlin Endgame remains the sternest test of the entire variation beginning with 3...Nf6, and a lot of theory has evolved here. Today's consensus is that Black will hold with accurate play in the Berlin Endgame, so players have moved on to the lines with 4.0-0 Nxe4 5.Re1, the modern main line, considered to be White's best try for an opening advantage, and advocated by Fabiano Caruana in his Chessbase Series on the Ruy Lopez opening.