Jung Won-Jun, a Korean who became the owner of a poor fief. In an attempt to make it prosper, he explores a dungeon. Orginal webtoon http://www.foxtoon.com/comic/maze_age_Z 

A powerful grand wizard named, “Raim” reappears after a millennium because of a failed experiment. While sets out to regain his lost tower, he meets “are” and “ere” who have been trafficked as slaves... a combination of a weird grand magician who only uses his wits to make money and the cute, lovable brother and sister of the miao tribe! Their endless adventure is beginning to unfold. Editorial staff’s comment Will Raim be able to regain his lost tower?! 

Manhwa you may like:
+ This is another ambitious work of Sung San Young, The Gamer
+ Tower of God
+ The God of High School