diff --git a/vpr7_x2p/vpr/SRC/device/mux_graph.h b/vpr7_x2p/vpr/SRC/device/mux_graph.h
new file mode 100644
index 000000000..1b57a9d58
--- /dev/null
+++ b/vpr7_x2p/vpr/SRC/device/mux_graph.h
@@ -0,0 +1,48 @@
+/**************************************************
+ * This file include a data structure to describe
+ * the internal structure of a multiplexer
+ * using a generic graph representation  
+ *************************************************/
+
+#ifndef MUX_ARCH_H
+#define MUX_ARCH_H
+
+#include <vector>
+#include "circuit_library.h"
+
+/* Strong Ids for MUXes */
+struct mux_id_tag;
+typedef vtr::StrongId<mux_id_tag> MuxId;
+
+class MuxGraph {
+  private: /* data types used only in this class */
+    enum e_mux_graph_node_type {
+      MUX_INPUT_NODE,
+      MUX_INTERNAL_NODE,
+      MUX_OUTPUT_NODE
+    };
+  private: /* Internal data */
+    std::vector<size_t> node_ids_;                        /* Unique ids for each node */
+    std::vector<size_t> node_levels_;                     /* at which level, each node belongs to */
+    std::vector<enum e_mux_graph_node_type> node_types_;  /* type of each node, input/output/internal */
+    std::vector<std::vector<size_t>> node_in_edges;       /* ids of incoming edges to each node */
+    std::vector<std::vector<size_t>> node_out_edges;      /* ids of outgoing edges from each node */
+
+    std::vector<size_t> edge_ids_;                        /* Unique ids for each edge */
+    std::vector<enum e_spice_model_pass_gate_logic_type> edge_types_; /* type of each edge: tgate/pass-gate */
+    std::vector<size_t> edge_sram_ids_;                   /* ids of SRAMs that control the edge */
+
+    std::vector<size_t> sram_ids_;                        /* ids of SRAMs (configuration memories) */
+
+    /* fast look-up */
+    typedef std::vector<std::vector<std::vector>>> NodeLookup;
+    mutable NodeLookup node_lookup_; /* [num_levels][num_branches][num_nodes_per_branch] */ 
+};
+
+class MuxLib {
+  private: /* Internal data */
+    vtr::vector<MuxId, MuxGraph> mux_graphs_; /* Graphs describing MUX internal structures */
+    vtr::vector<MuxId, CircuitModelId> circuit_model_ids_; /* ids in the circuit library, each MUX graph belongs to*/
+}
+
+#endif